Red Hat Enterprise Linux 5 Global File System. Red Hat Global File System Edition 4

Transcription

1 Red Hat Enterprise Linux 5 Global File System Red Hat Global File System Edition 4

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3 Red Hat Enterprise Linux 5 Global File System Red Hat Global File System Edition 4

4 Legal Notice Copyright 2014 Red Hat, Inc. This document is licensed by Red Hat under the Creative Commons Attribution-ShareAlike 3.0 Unported License. If you distribute this document, or a modified version of it, you must provide attribution to Red Hat, Inc. and provide a link to the original. If the document is modified, all Red Hat trademarks must be removed. Red Hat, as the licensor of this document, waives the right to enforce, and agrees not to assert, Section 4d of CC-BY-SA to the fullest extent permitted by applicable law. Red Hat, Red Hat Enterprise Linux, the Shadowman logo, JBoss, OpenShift, Fedora, the Infinity logo, and RHCE are trademarks of Red Hat, Inc., registered in the United States and other countries. Linux is the registered trademark of Linus Torvalds in the United States and other countries. Java is a registered trademark of Oracle and/or its affiliates. XFS is a trademark of Silicon Graphics International Corp. or its subsidiaries in the United States and/or other countries. MySQL is a registered trademark of MySQL AB in the United States, the European Union and other countries. Node.js is an official trademark of Joyent. Red Hat Software Collections is not formally related to or endorsed by the official Joyent Node.js open source or commercial project. The OpenStack Word Mark and OpenStack logo are either registered trademarks/service marks or trademarks/service marks of the OpenStack Foundation, in the United States and other countries and are used with the OpenStack Foundation's permission. We are not affiliated with, endorsed or sponsored by the OpenStack Foundation, or the OpenStack community. All other trademarks are the property of their respective owners. Abstract This book provides information about configuring, and maintaining Red Hat GFS (Red Hat Global File System) for Red Hat Enterprise Linux 5.

5 Table of Contents Table of Contents. Chapter Introduction Audience Related Documentation 2. Chapter GFS.... Overview New and Changed Features Performance, Scalability, and Economy GFS Software Components Before Setting Up GFS 7. Chapter Getting Started Prerequisite Tasks Initial Setup Tasks 9. Chapter Managing GFS Creating a File System Mounting a File System Unmounting a File System Special Considerations when Mounting GFS File Systems Displaying GFS Tunable Parameters GFS Quota Management Growing a File System Adding Journals to a File System Direct I/O Data Journaling Configuring atime Updates Suspending Activity on a File System Displaying Extended GFS Information and Statistics Repairing a File System Context-Dependent Path Names The GFS Withdraw Function 45. Appendix A... Revision History Index

6 Global File System Chapter 1. Introduction The Global File System Configuration and Administration document provides information about configuring and maintaining Red Hat GFS (Red Hat Global File System). A GFS file system can be implemented in a standalone system or as part of a cluster configuration. For information about Red Hat Cluster Suite refer to Red Hat Cluster Suite Overview and Configuring and Managing a Red Hat Cluster. HTML and PDF versions of all the official Red Hat Enterprise Linux manuals and release notes are available online at Audience This book is intended primarily for Linux system administrators who are familiar with the following activities: Linux system administration procedures, including kernel configuration Installation and configuration of shared storage networks, such as Fibre Channel SANs 1.2. Related Documentation For more information about using Red Hat Enterprise Linux, refer to the following resources: Red Hat Enterprise Linux Installation Guide Provides information regarding installation of Red Hat Enterprise Linux 5. Red Hat Enterprise Linux Deployment Guide Provides information regarding the deployment, configuration and administration of Red Hat Enterprise Linux 5. For more information about Red Hat Cluster Suite for Red Hat Enterprise Linux 5, refer to the following resources: Red Hat Cluster Suite Overview Provides a high level overview of the Red Hat Cluster Suite. Configuring and Managing a Red Hat Cluster Provides information about installing, configuring and managing Red Hat Cluster components. Logical Volume Manager Administration Provides a description of the Logical Volume Manager (LVM), including information on running LVM in a clustered environment. Global File System 2: Configuration and Administration Provides information about installing, configuring, and maintaining Red Hat GFS2 (Red Hat Global File System 2). Using Device-Mapper Multipath Provides information about using the Device-Mapper Multipath feature of Red Hat Enterprise Linux 5. Using GNBD with Global File System Provides an overview on using Global Network Block Device (GNBD) with Red Hat GFS. Linux Virtual Server Administration Provides information on configuring high-performance systems and services with the Linux Virtual Server (LVS). Red Hat Cluster Suite Release Notes Provides information about the current release of Red Hat Cluster Suite. Red Hat Cluster Suite documentation and other Red Hat documents are available in HTML, PDF, and RPM versions on the Red Hat Enterprise Linux Documentation CD and online at 2

7 Chapter 2. GFS Overview Chapter 2. GFS Overview The Red Hat GFS file system is a native file system that interfaces directly with the Linux kernel file system interface (VFS layer). When implemented as a cluster file system, GFS employs distributed metadata and multiple journals. Red Hat supports the use of GFS file systems only as implemented in Red Hat Cluster Suite. Note Although a GFS file system can be implemented in a standalone system or as part of a cluster configuration, for the Red Hat Enterprise Linux 5.5 release and later Red Hat does not support the use of GFS as a single-node file system. Red Hat does support a number of high-performance single node file systems which are optimized for single node and thus have generally lower overhead than a cluster filesystem. Red Hat recommends using these file systems in preference to GFS in cases where only a single node needs to mount the file system. Red Hat will continue to support single-node GFS file systems for existing customers. Note Red Hat does not support using GFS for cluster file system deployments greater than 16 nodes. GFS is based on a 64-bit architecture, which can theoretically accommodate an 8 EB file system. However, the current supported maximum size of a GFS file system for 64-bit hardware is 100 TB. The current supported maximum size of a GFS file system for 32-bit hardware is 16 TB. If your system requires larger GFS file systems, contact your Red Hat service representative. When determining the size of your file system, you should consider your recovery needs. Running the gfs_fsck command on a very large file system can take a long time and consume a large amount of memory. Additionally, in the event of a disk or disk-subsytem failure, recovery time is limited by the speed of your backup media. For information on the amount of memory the gfs_fsck command requires, see Section 4.14, Repairing a File System. When configured in a Red Hat Cluster Suite, Red Hat GFS nodes can be configured and managed with Red Hat Cluster Suite configuration and management tools. Red Hat GFS then provides data sharing among GFS nodes in a Red Hat cluster, with a single, consistent view of the file system name space across the GFS nodes. This allows processes on different nodes to share GFS files in the same way that processes on the same node can share files on a local file system, with no discernible difference. For information about Red Hat Cluster Suite refer to Configuring and Managing a Red Hat Cluster. While a GFS file system may be used outside of LVM, Red Hat supports only GFS file systems that are created on a CLVM logical volume. CLVM is a cluster-wide implementation of LVM, enabled by the CLVM daemon clvmd, which manages LVM logical volumes in a Red Hat Cluster Suite cluster. The daemon makes it possible to use LVM2 to manage logical volumes across a cluster, allowing all nodes in the cluster to share the logical volumes. For information on the LVM volume manager, see Logical Volume Manager Administration 3

8 Global File System Note When you configure a GFS file system as a cluster file system, you must ensure that all nodes in the cluster have access to the shared file system. Asymmetric cluster configurations in which some nodes have access to the file system and others do not are not supported. This chapter provides some basic, abbreviated information as background to help you understand GFS. It contains the following sections: Section 2.1, New and Changed Features Section 2.2, Performance, Scalability, and Economy Section 2.3, GFS Software Components Section 2.4, Before Setting Up GFS 2.1. New and Changed Features This section lists new and changed features included with the initial release of Red Hat Enterprise Linux 5. GULM (Grand Unified Lock Manager) is not supported in Red Hat Enterprise Linux 5. If your GFS file systems use the GULM lock manager, you must convert the file systems to use the DLM lock manager. This is a two-part process. While running Red Hat Enterprise Linux 4, convert your GFS file systems to use the DLM lock manager. Upgrade your operating system to Red Hat Enterprise Linux 5, converting the lock manager to DLM when you do. For information on upgrading to Red Hat Enterprise Linux 5 and converting GFS file systems to use the DLM lock manager, see Configuring and Managing a Red Hat Cluster. Documentation for Red Hat Cluster Suite for Red Hat Enterprise Linux 5 has been expanded and reorganized. For information on the available documents, see Section 1.2, Related Documentation Performance, Scalability, and Economy You can deploy GFS in a variety of configurations to suit your needs for performance, scalability, and economy. For superior performance and scalability, you can deploy GFS in a cluster that is connected directly to a SAN. For more economical needs, you can deploy GFS in a cluster that is connected to a LAN with servers that use GNBD (Global Network Block Device). The following sections provide examples of how GFS can be deployed to suit your needs for performance, scalability, and economy: Section 2.2.1, Superior Performance and Scalability Section 2.2.2, Economy and Performance 4

9 Chapter 2. GFS Overview Note The deployment examples in this chapter reflect basic configurations; your needs might require a combination of configurations shown in the examples Superior Performance and Scalability You can obtain the highest shared-file performance when applications access storage directly. The GFS SAN configuration in Figure 2.1, GFS with a SAN provides superior file performance for shared files and file systems. Linux applications run directly on GFS nodes. Without file protocols or storage servers to slow data access, performance is similar to individual Linux servers with directly connected storage; yet, each GFS application node has equal access to all data files. GFS supports up to 125 GFS nodes. Figure 2.1. GFS with a SAN Economy and Performance Multiple Linux client applications on a LAN can share the same SAN-based data as shown in Figure 2.2, GFS and GNBD with a SAN. SAN block storage is presented to network clients as block storage devices by GNBD servers. From the perspective of a client application, storage is accessed as if it were directly attached to the server in which the application is running. Stored data is actually on the SAN. Storage devices and data can be equally shared by network client applications. File locking and sharing functions are handled by GFS for each network client. Note Clients implementing ext2 and ext3 file systems can be configured to access their own dedicated slice of SAN storage. 5

10 Global File System Figure 2.2. GFS and GNBD with a SAN Figure 2.3, GFS and GNBD with Directly Connected Storage shows how Linux client applications can take advantage of an existing Ethernet topology to gain shared access to all block storage devices. Client data files and file systems can be shared with GFS on each client. Application failover can be fully automated with Red Hat Cluster Suite. Figure 2.3. GFS and GNBD with Directly Connected Storage 6

11 Chapter 2. GFS Overview 2.3. GFS Software Components Table 2.1, GFS Software Subsystem Components summarizes the GFS software components. Table 2.1. GFS Software Subsystem Components Software Component gfs.ko lock_dlm.ko lock_nolock.ko Description Kernel module that implements the GFS file system and is loaded on GFS cluster nodes. A lock module that implements DLM locking for GFS. It plugs into the lock harness, lock_harness.ko and communicates with the DLM lock manager in Red Hat Cluster Suite. A lock module for use when GFS is used as a local file system only. It plugs into the lock harness, lock_harness.ko and provides local locking Before Setting Up GFS Before you install and set up GFS, note the following key characteristics of your GFS file systems: GFS nodes Determine which nodes in the Red Hat Cluster Suite will mount the GFS file systems. Number of file systems Determine how many GFS file systems to create initially. (More file systems can be added later.) File system name Determine a unique name for each file system. Each file system name is required in the form of a parameter variable. For example, this book uses file system names mydata1 and mydata2 in some example procedures. File system size GFS is based on a 64-bit architecture, which can theoretically accommodate an 8 EB file system. However, the current supported maximum size of a GFS file system for 64-bit hardware is 100 TB. The current supported maximum size of a GFS file system for 32-bit hardware is 16 TB. If your system requires larger GFS file systems, contact your Red Hat service representative. When determining the size of your file system, you should consider your recovery needs. Running the gfs_fsck command on a very large file system can take a long time and consume a large amount of memory. Additionally, in the event of a disk or disk-subsytem failure, recovery time is limited by the speed of your backup media. For information on the amount of memory the gfs_fsck command requires, see Section 4.14, Repairing a File System. Journals Determine the number of journals for your GFS file systems. One journal is required for each node that mounts a GFS file system. Make sure to account for additional journals needed for future expansion, as you cannot add journals dynamically to a GFS file system. GNBD server nodes 7

12 Global File System If you are using GNBD, determine how many GNBD server nodes are needed. Note the hostname and IP address of each GNBD server node for setting up GNBD clients later. For information on using GNBD with GFS, see the Using GNBD with Global File System document. Storage devices and partitions Determine the storage devices and partitions to be used for creating logical volumes (via CLVM) in the file systems. Note You may see performance problems with GFS when many create and delete operations are issued from more than one node in the same directory at the same time. If this causes performance problems in your system, you should localize file creation and deletions by a node to directories specific to that node as much as possible. 8

13 Chapter 3. Getting Started Chapter 3. Getting Started This chapter describes procedures for initial setup of GFS and contains the following sections: Section 3.1, Prerequisite Tasks Section 3.2, Initial Setup Tasks 3.1. Prerequisite Tasks You should complete the following tasks before setting up Red Hat GFS: Make sure that you have noted the key characteristics of the GFS nodes (refer to Section 2.4, Before Setting Up GFS ). Make sure that the clocks on the GFS nodes are synchronized. It is recommended that you use the Network Time Protocol (NTP) software provided with your Red Hat Enterprise Linux distribution. Note The system clocks in GFS nodes must be within a few minutes of each other to prevent unnecessary inode time-stamp updating. Unnecessary inode time-stamp updating severely impacts cluster performance. In order to use GFS in a clustered environment, you must configure your system to use the Clustered Logical Volume Manager (CLVM), a set of clustering extensions to the LVM Logical Volume Manager. In order to use CLVM, the Red Hat Cluster Suite software, including the clvmd daemon, must be running. For information on using CLVM, see Logical Volume Manager Administration. For information on installing and administering Red Hat Cluster Suite, see Cluster Administration Initial Setup Tasks Initial GFS setup consists of the following tasks: 1. Setting up logical volumes 2. Making a GFS files system 3. Mounting file systems Follow these steps to set up GFS initially. 1. Using LVM, create a logical volume for each Red Hat GFS file system. Note You can use init.d scripts included with Red Hat Cluster Suite to automate activating and deactivating logical volumes. For more information about init.d scripts, refer to Configuring and Managing a Red Hat Cluster. 9

14 Global File System 2. Create GFS file systems on logical volumes created in Step 1. Choose a unique name for each file system. For more information about creating a GFS file system, refer to Section 4.1, Creating a File System. You can use either of the following formats to create a clustered GFS file system: gfs_mkfs -p lock_dlm -t ClusterName:FSName -j NumberJournals BlockDevice mkfs -t gfs -p lock_dlm -t LockTableName -j NumberJournals BlockDevice You can use either of the following formats to create a local GFS file system: gfs_mkfs -p lock_nolock -j NumberJournals BlockDevice mkfs -t gfs -p lock_nolock -j NumberJournals BlockDevice For more information on creating a GFS file system, see Section 4.1, Creating a File System. 3. At each node, mount the GFS file systems. For more information about mounting a GFS file system, see Section 4.2, Mounting a File System. Command usage: mount BlockDevice MountPoint mount -o acl BlockDevice MountPoint The -o acl mount option allows manipulating file ACLs. If a file system is mounted without the -o acl mount option, users are allowed to view ACLs (with getfacl), but are not allowed to set them (with setfacl). Note You can use init.d scripts included with Red Hat Cluster Suite to automate mounting and unmounting GFS file systems. For more information about init.d scripts, refer to Configuring and Managing a Red Hat Cluster. 10

15 Chapter 4. Managing GFS Chapter 4. Managing GFS This chapter describes the tasks and commands for managing GFS and consists of the following sections: Section 4.1, Creating a File System Section 4.2, Mounting a File System Section 4.3, Unmounting a File System Section 4.4, Special Considerations when Mounting GFS File Systems Section 4.5, Displaying GFS Tunable Parameters Section 4.6, GFS Quota Management Section 4.7, Growing a File System Section 4.8, Adding Journals to a File System Section 4.9, Direct I/O Section 4.10, Data Journaling Section 4.11, Configuring atime Updates Section 4.12, Suspending Activity on a File System Section 4.13, Displaying Extended GFS Information and Statistics Section 4.14, Repairing a File System Section 4.15, Context-Dependent Path Names Section 4.16, The GFS Withdraw Function 4.1. Creating a File System You can create a GFS file system with the gfs_mkfs command. A file system is created on an activated LVM volume. The following information is required to execute the gfs_mkfs command: Lock protocol/module name. The lock protocol for a cluster is lock_dlm. The lock protocol when GFS is acting as a local file system (one node only) is lock_nolock. Cluster name (when running as part of a cluster configuration). Number of journals (one journal required for each node that may be mounting the file systema.) Make sure to account for additional journals needed for future expansion, as you cannot add journals dynamically to a GFS file system. When creating a GFS file system, you can use the gfs_mkfs directly, or you can use the mkfs command with the -t parameter specifying a file system of type gfs, followed by the gfs file system options. 11

16 Global File System Note Once you have created a GFS file system with the gfs_mkfs command, you cannot decrease the size of the file system. You can, however, increase the size of an existing file system with the gfs_grow command, as described in Section 4.7, Growing a File System. Usage When creating a clustered GFS file system, you can use either of the following formats: gfs_mkfs -p LockProtoName -t LockTableName -j NumberJournals BlockDevice mkfs -t gfs -p LockProtoName -t LockTableName -j NumberJournals BlockDevice When creating a local file system, you can use either of the following formats: Note For the Red Hat Enterprise Linux 5.5 release and later Red Hat does not support the use of GFS as a single-node file system. Red Hat will continue to support single-node GFS file systems for existing customers. gfs_mkfs -p LockProtoName -j NumberJournals BlockDevice mkfs -t gfs -p LockProtoName -j NumberJournals BlockDevice Warning Make sure that you are very familiar with using the LockProtoName and LockTableName parameters. Improper use of the LockProtoName and LockTableName parameters may cause file system or lock space corruption. LockProtoName Specifies the name of the locking protocol to use. The lock protocol for a cluster is lock_dlm. The lock protocol when GFS is acting as a local file system (one node only) is lock_nolock. LockTableName This parameter is specified for GFS file system in a cluster configuration. It has two parts separated by a colon (no spaces) as follows: ClusterName:FSName ClusterName, the name of the Red Hat cluster for which the GFS file system is being created. FSName, the file system name, can be 1 to 16 characters long, and the name must be unique among all file systems in the cluster. 12

17 Chapter 4. Managing GFS NumberJournals Specifies the number of journals to be created by the gfs_mkfs command. One journal is required for each node that mounts the file system. (More journals than are needed can be specified at creation time to allow for future expansion.) BlockDevice Specifies a volume. Examples In these examples, lock_dlm is the locking protocol that the file system uses, since this is a clustered file system. The cluster name is alpha, and the file system name is mydata1. The file system contains eight journals and is created on /dev/vg01/lvol0. [root@ask-07 ~]# gfs_mkfs -p lock_dlm -t alpha:mydata1 -j 8 /dev/vg01/lvol0 This will destroy any data on /dev/vg01/lvol0. Are you sure you want to proceed? [y/n] y Device: /dev/vg01/lvol0 Blocksize: 4096 Filesystem Size: Journals: 8 Resource Groups: 2082 Locking Protocol: lock_dlm Lock Table: alpha:mydata1 Syncing... All Done [root@ask-07 ~]# mkfs -t gfs -p lock_dlm -t alpha:mydata1 -j 8 /dev/vg01/lvol0 This will destroy any data on /dev/vg01/lvol0. Are you sure you want to proceed? [y/n] y Device: /dev/vg01/lvol0 Blocksize: 4096 Filesystem Size: Journals: 8 Resource Groups: 2082 Locking Protocol: lock_dlm Lock Table: alpha:mydata1 Syncing... All Done In these examples, a second lock_dlm file system is made, which can be used in cluster alpha. The file system name is mydata2. The file system contains eight journals and is created on /dev/vg01/lvol1. gfs_mkfs -p lock_dlm -t alpha:mydata2 -j 8 /dev/vg01/lvol1 13

18 Global File System mkfs -t gfs -p lock_dlm -t alpha:mydata2 -j 8 /dev/vg01/lvol1 Complete Options Table 4.1, Command Options: gfs_mkfs describes the gfs_mkfs command options. Table 4.1. Command Options: gfs_mkfs Flag Parameter Description -b BlockSize Sets the file system block size to BlockSize. Default block size is 4096 bytes. -D Enables debugging output. -h Help. Displays available options. -J MegaBytes Specifies the size of the journal in megabytes. Default journal size is 128 megabytes. The minimum size is 32 megabytes. -j Number Specifies the number of journals to be created by the gfs_mkfs command. One journal is required for each node that mounts the file system. Note: More journals than are needed can be specified at creation time to allow for future expansion. -p LockProtoName Specifies the name of the locking protocol to use. Recognized locking protocols include: lock_dlm The standard locking module, required for a clustered file system. lock_nolock Used when GFS is acting as a local file system (one node only). -O Prevents the gfs_mkfs command from asking for confirmation before writing the file system. -q Quiet. Do not display anything. -r MegaBytes Specifies the size of the resource groups in megabytes. Default resource group size is 256 megabytes. -s Blocks Specifies the journal-segment size in file system blocks. -t LockTableName Used in a clustered file system. This parameter has two parts separated by a colon (no spaces) as follows: ClusterName:FSName. ClusterName is the name of the Red Hat cluster for which the GFS file system is being created. The cluster name is set in the /etc/cluster/cluster.conf file via the Cluster Configuration Tool and displayed at the Cluster Status Tool in the Red Hat Cluster Suite cluster management GUI. FSName, the file system name, can be 1 to 16 characters in length, and the name must be unique among all file systems in the cluster. 14

19 Chapter 4. Managing GFS Flag Parameter Description -V Displays command version information Mounting a File System Before you can mount a GFS file system, the file system must exist (refer to Section 4.1, Creating a File System ), the volume where the file system exists must be activated, and the supporting clustering and locking systems must be started (refer to Chapter 3, Getting Started and Configuring and Managing a Red Hat Cluster. After those requirements have been met, you can mount the GFS file system as you would any Linux file system. To manipulate file ACLs, you must mount the file system with the -o acl mount option. If a file system is mounted without the -o acl mount option, users are allowed to view ACLs (with getfacl), but are not allowed to set them (with setfacl). Usage Mounting Without ACL Manipulation mount BlockDevice MountPoint Mounting With ACL Manipulation mount -o acl BlockDevice MountPoint -o acl GFS-specific option to allow manipulating file ACLs. BlockDevice Specifies the block device where the GFS file system resides. MountPoint Specifies the directory where the GFS file system should be mounted. Example In this example, the GFS file system on /dev/vg01/lvol0 is mounted on the /mydata1 directory. mount /dev/vg01/lvol0 /mydata1 Complete Usage mount BlockDevice MountPoint -o option The -o option argument consists of GFS-specific options (refer to Table 4.2, GFS-Specific Mount Options ) or acceptable standard Linux mount -o options, or a combination of both. Multiple option parameters are separated by a comma and no spaces. 15

20 Global File System Note The mount command is a Linux system command. In addition to using GFS-specific options described in this section, you can use other, standard, mount command options (for example, -r). For information about other Linux mount command options, see the Linux mount man page. Table 4.2, GFS-Specific Mount Options describes the available GFS-specific -o option values that can be passed to GFS at mount time. Note This table includes descriptions of options that are used with local file systems only For the Red Hat Enterprise Linux 5.5 release and later Red Hat does not support the use of GFS as a single-node file system. Red Hat will continue to support single-node GFS file systems for existing customers. Table 4.2. GFS-Specific Mount Options Option acl ignore_local_fs Caution: This option should not be used when GFS file systems are shared. localcaching Caution: This option should not be used when GFS file systems are shared. Description Allows manipulating file ACLs. If a file system is mounted without the acl mount option, users are allowed to view ACLs (with getfacl), but are not allowed to set them (with setfacl). Forces GFS to treat the file system as a multihost file system. By default, using lock_nolock automatically turns on the localcaching and localflocks flags. Tells GFS that it is running as a local file system. GFS can then turn on selected optimization capabilities that are not available when running in cluster mode. The localcaching flag is automatically turned on by lock_nolock. 16

21 Chapter 4. Managing GFS Option localflocks Caution: This option should not be used when GFS file systems are shared. Description Tells GFS to let the VFS (virtual file system) layer do all flock and fcntl. The localflocks flag is automatically turned on by lock_nolock. Note that the localflocks mount option affects only advisory fcntl()/posix locks and flock locks that are issued by applications. The internal locking that ensures coherency of data across the cluster by means of GFS's glock abstraction is separate from and not affected by the localflocks setting. If you are unsure whether an application uses fcntl()/posix locks and thus requires that you mount your file system with the localflocks, you can use the strace utility to print out the system calls that are made during a test run of the application. Look for fcntl calls that have F_GETLK, F_SETLK, or F_SETLKW as the cmd argument. Note that GFS does not currently support either leases or mandatory locking. lockproto=lockmodulename locktable=locktablename oopses_ok Allows the user to specify which locking protocol to use with the file system. If LockModuleName is not specified, the locking protocol name is read from the file system superblock. For a clustered file system, allows the user to specify which locking table to use with the file system. This option allows a GFS node to not panic when an oops occurs. (By default, a GFS node panics when an oops occurs, causing the file system used by that node to stall for other GFS nodes.) A GFS node not panicking when an oops occurs minimizes the failure on other GFS nodes using the file system that the failed node is using. There may be circumstances where you do not want to use this option for example, when you need more detailed troubleshooting information. Use this option with care. Note: This option is turned on automatically if lock_nolock locking is specified; however, you can override it by using the ignore_local_fs option. upgrade errors=panic withdraw Upgrade the on-disk format of the file system so that it can be used by newer versions of GFS. When errors=panic is specified, file system errors will cause a kernel panic. The default behavior, which is the same as specifying errors=withdraw, is for the system to withdraw from the file system and make it inaccessible until the next reboot; in some cases the system may remain running. For information on the GFS withdraw function, see Section 4.16, The GFS Withdraw Function Unmounting a File System 17

22 Global File System The GFS file system can be unmounted the same way as any Linux file system by using the umount command. Note The umount command is a Linux system command. Information about this command can be found in the Linux umount command man pages. Usage umount MountPoint MountPoint Specifies the directory where the GFS file system should be mounted Special Considerations when Mounting GFS File Systems GFS file systems that have been mounted manually rather than automatically through an entry in the fstab file will not be known to the system when file systems are unmounted at system shutdown. As a result, the GFS script will not unmount the GFS file system. After the GFS shutdown script is run, the standard shutdown process kills off all remaining user processes, including the cluster infrastructure, and tries to unmount the file system. This unmount will fail without the cluster infrastructure and the system will hang. To prevent the system from hanging when the GFS file systems are unmounted, you should do one of the following: Always use an entry in the fstab file to mount the GFS file system. If a GFS file system has been mounted manually with the mount command, be sure to unmount the file system manually with the umount command before rebooting or shutting down the system. If your file system hangs while it is being unmounted during system shutdown under these circumstances, perform a hardware reboot. It is unlikely that any data will be lost since the file system is synced earlier in the shutdown process Displaying GFS Tunable Parameters There are a variety of parameters associated with a GFS file system that you can modify with the gfs_tool settune command. Some of these parameters are used to administer GFS quotas: quota_quantum, quota_enforce, quota_account, and atime_quantum. These parameters are described in Section 4.6, GFS Quota Management, along with examples of how to modify them. Parameters that you set with the gfs_tool settune command must be set on each node each time the file system is mounted. These parameters are not persistent across mounts. 18

23 Chapter 4. Managing GFS Note The majority of the tunable parameters are internal parameters. They are intended for development purposes only and should not be changed. The gfs_tool gettune command displays a listing of the current values of the GFS tunable parameters. Usage Display Tunable Parameters gfs_tool gettune MountPoint MountPoint Specifies the directory where the GFS file system is mounted. Examples In this example, all GFS tunable parameters for the file system on the mount point /mnt/gfs are displayed. [root@tng3-1]# gfs_tool gettune /mnt/gfs ilimit1 = 100 ilimit1_tries = 3 ilimit1_min = 1 ilimit2 = 500 ilimit2_tries = 10 ilimit2_min = 3 demote_secs = 300 incore_log_blocks = 1024 jindex_refresh_secs = 60 depend_secs = 60 scand_secs = 5 recoverd_secs = 60 logd_secs = 1 quotad_secs = 5 inoded_secs = 15 glock_purge = 0 quota_simul_sync = 64 quota_warn_period = 10 atime_quantum = 3600 quota_quantum = 60 quota_scale = (1, 1) quota_enforce = 1 quota_account = 1 new_files_jdata = 0 new_files_directio = 0 max_atomic_write = max_readahead = lockdump_size = stall_secs = 600 complain_secs = 10 reclaim_limit =

24 Global File System entries_per_readdir = 32 prefetch_secs = 10 statfs_slots = 64 max_mhc = greedy_default = 100 greedy_quantum = 25 greedy_max = 250 rgrp_try_threshold = 100 statfs_fast = GFS Quota Management File-system quotas are used to limit the amount of file system space a user or group can use. A user or group does not have a quota limit until one is set. GFS keeps track of the space used by each user and group even when there are no limits in place. GFS updates quota information in a transactional way so system crashes do not require quota usages to be reconstructed. To prevent a performance slowdown, a GFS node synchronizes updates to the quota file only periodically. The "fuzzy" quota accounting can allow users or groups to slightly exceed the set limit. To minimize this, GFS dynamically reduces the synchronization period as a "hard" quota limit is approached. GFS uses its gfs_quota command to manage quotas. Other Linux quota facilities cannot be used with GFS Setting Quotas Two quota settings are available for each user ID (UID) or group ID (GID): a hard limit and a warn limit. A hard limit is the amount of space that can be used. The file system will not let the user or group use more than that amount of disk space. A hard limit value of zero means that no limit is enforced. A warn limit is usually a value less than the hard limit. The file system will notify the user or group when the warn limit is reached to warn them of the amount of space they are using. A warn limit value of zero means that no limit is enforced. Limits are set using the gfs_quota command. The command only needs to be run on a single node where GFS is mounted. Usage Setting Quotas, Hard Limit gfs_quota limit -u User -l Size -f MountPoint gfs_quota limit -g Group -l Size -f MountPoint Setting Quotas, Warn Limit gfs_quota warn -u User -l Size -f MountPoint gfs_quota warn -g Group -l Size -f MountPoint User 20

25 Chapter 4. Managing GFS Group Size A user ID to limit or warn. It can be either a user name from the password file or the UID number. A group ID to limit or warn. It can be either a group name from the group file or the GID number. Specifies the new value to limit or warn. By default, the value is in units of megabytes. The additional -k, -s and -b flags change the units to kilobytes, sectors, and file system blocks, respectively. MountPoint Specifies the GFS file system to which the actions apply. Examples This example sets the hard limit for user Bert to 1024 megabytes (1 gigabyte) on file system /gfs. gfs_quota limit -u Bert -l f /gfs This example sets the warn limit for group ID 21 to 50 kilobytes on file system /gfs. gfs_quota warn -g 21 -l 50 -k -f /gfs Displaying Quota Limits and Usage Quota limits and current usage can be displayed for a specific user or group using the gfs_quota get command. The entire contents of the quota file can also be displayed using the gfs_quota list command, in which case all IDs with a non-zero hard limit, warn limit, or value are listed. Usage Displaying Quota Limits for a User gfs_quota get -u User -f MountPoint Displaying Quota Limits for a Group gfs_quota get -g Group -f MountPoint Displaying Entire Quota File gfs_quota list -f MountPoint User Group A user ID to display information about a specific user. It can be either a user name from the password file or the UID number. 21

26 Global File System A group ID to display information about a specific group. It can be either a group name from the group file or the GID number. MountPoint Specifies the GFS file system to which the actions apply. Command Output GFS quota information from the gfs_quota command is displayed as follows: user User: limit:limitsize warn:warnsize value:value group Group: limit:limitsize warn:warnsize value:value The LimitSize, WarnSize, and Value numbers (values) are in units of megabytes by default. Adding the -k, -s, or -b flags to the command line change the units to kilobytes, sectors, or file system blocks, respectively. User Group A user name or ID to which the data is associated. A group name or ID to which the data is associated. LimitSize Value The hard limit set for the user or group. This value is zero if no limit has been set. The actual amount of disk space used by the user or group. Comments When displaying quota information, the gfs_quota command does not resolve UIDs and GIDs into names if the -n option is added to the command line. Space allocated to GFS's hidden files can be left out of displayed values for the root UID and GID by adding the -d option to the command line. This is useful when trying to match the numbers from gfs_quota with the results of a du command. Examples This example displays quota information for all users and groups that have a limit set or are using any disk space on file system /gfs. [root@ask-07 ~]# gfs_quota list -f /gfs user root: limit: 0.0 warn: 0.0 value: 0.2 user moe: limit: warn: 0.0 value: 0.0 group root: limit: 0.0 warn: 0.0 value: 0.2 group stooges: limit: 0.0 warn: 0.0 value:

27 Chapter 4. Managing GFS This example displays quota information in sectors for group users on file system /gfs. ~]# gfs_quota get -g users -f /gfs -s group users: limit: 0 warn: 96 value: Synchronizing Quotas GFS stores all quota information in its own internal file on disk. A GFS node does not update this quota file for every file system write; rather, it updates the quota file once every 60 seconds. This is necessary to avoid contention among nodes writing to the quota file, which would cause a slowdown in performance. As a user or group approaches their quota limit, GFS dynamically reduces the time between its quota-file updates to prevent the limit from being exceeded. The normal time period between quota synchronizations is a tunable parameter, quota_quantum, and can be changed using the gfs_tool command. By default, the time period is 60 seconds. Also, the quota_quantum parameter must be set on each node and each time the file system is mounted. (Changes to the quota_quantum parameter are not persistent across unmounts.) To see the current values of the GFS tunable parameters, including quota_quantum, you can use the gfs_tool gettune, as described in Section 4.5, Displaying GFS Tunable Parameters. You can use the gfs_quota sync command to synchronize the quota information from a node to the ondisk quota file between the automatic updates performed by GFS. Usage Synchronizing Quota Information gfs_quota sync -f MountPoint MountPoint Specifies the GFS file system to which the actions apply. Tuning the Time Between Synchronizations gfs_tool settune MountPoint quota_quantum Seconds MountPoint Specifies the GFS file system to which the actions apply. Seconds Specifies the new time period between regular quota-file synchronizations by GFS. Smaller values may increase contention and slow down performance. Examples This example synchronizes the quota information from the node it is run on to file system /gfs. gfs_quota sync -f /gfs 23

28 Global File System This example changes the default time period between regular quota-file updates to one hour (3600 seconds) for file system /gfs on a single node. gfs_tool settune /gfs quota_quantum Disabling/Enabling Quota Enforcement Enforcement of quotas can be disabled for a file system without clearing the limits set for all users and groups. Enforcement can also be enabled. Disabling and enabling of quota enforcement is done by changing a tunable parameter, quota_enforce, with the gfs_tool command. The quota_enforce parameter must be disabled or enabled on each node where quota enforcement should be disabled/enabled. Each time the file system is mounted, enforcement is enabled by default. (Disabling is not persistent across unmounts.) To see the current values of the GFS tunable parameters, including quota_enforce, you can use the gfs_tool gettune, as described in Section 4.5, Displaying GFS Tunable Parameters. Usage gfs_tool settune MountPoint quota_enforce {0 1} MountPoint Specifies the GFS file system to which the actions apply. quota_enforce {0 1} 0 = disabled 1 = enabled Comments A value of 0 disables enforcement. Enforcement can be enabled by running the command with a value of 1 (instead of 0) as the final command line parameter. Even when GFS is not enforcing quotas, it still keeps track of the file system usage for all users and groups so that quota-usage information does not require rebuilding after re-enabling quotas. Examples This example disables quota enforcement on file system /gfs. gfs_tool settune /gfs quota_enforce 0 This example enables quota enforcement on file system /gfs. gfs_tool settune /gfs quota_enforce Disabling/Enabling Quota Accounting By default, quota accounting is enabled; therefore, GFS keeps track of disk usage for every user and group even when no quota limits have been set. Quota accounting incurs unnecessary overhead if quotas are not used. You can disable quota accounting completely by setting the quota_account tunable parameter to 0. This must be done on each node and after each mount. (The 0 setting is not persistent across unmounts.) 24

29 Chapter 4. Managing GFS Quota accounting can be enabled by setting the quota_account tunable parameter to 1. To see the current values of the GFS tunable parameters, including quota_account, you can use the gfs_tool gettune, as described in Section 4.5, Displaying GFS Tunable Parameters. Usage gfs_tool settune MountPoint quota_account {0 1} MountPoint Specifies the GFS file system to which the actions apply. quota_account {0 1} 0 = disabled 1 = enabled Comments To enable quota accounting on a file system, the quota_account parameter must be set back to 1. Afterward, the GFS quota file must be initialized to account for all current disk usage for users and groups on the file system. The quota file is initialized by running: gfs_quota init -f MountPoint. Note Initializing the quota file requires scanning the entire file system and may take a long time. To see the current values of the GFS tunable parameters, including quota_account, you can use the gfs_tool gettune, as described in Section 4.5, Displaying GFS Tunable Parameters. Examples This example disables quota accounting on file system /gfs on a single node. gfs_tool settune /gfs quota_account 0 This example enables quota accounting on file system /gfs on a single node and initializes the quota file. # gfs_tool settune /gfs quota_account 1 # gfs_quota init -f /gfs 4.7. Growing a File System The gfs_grow command is used to expand a GFS file system after the device where the file system resides has been expanded. Running a gfs_grow command on an existing GFS file system fills all spare space between the current end of the file system and the end of the device with a newly initialized GFS file system extension. When the fill operation is completed, the resource index for the file system is updated. All nodes in the cluster can then use the extra storage space that has been added. 25

30 Global File System The gfs_grow command must be run on a mounted file system, but only needs to be run on one node in a cluster. All the other nodes sense that the expansion has occurred and automatically start using the new space. To verify that the changes were successful, use the gfs_grow command with the -T (test) and -v (verbose) flags. Running the command with those flags displays the current state of the mounted GFS file system. Note Once you have created a GFS file system with the gfs_mkfs command, you cannot decrease the size of the file system. Usage gfs_grow MountPoint MountPoint Specifies the GFS file system to which the actions apply. Comments Before running the gfs_grow command: Back up important data on the file system. Display the volume that is used by the file system to be expanded by running a df MountPoint command. Expand the underlying cluster volume with LVM. For information on administering LVM volumes, see Logical Volume Manager Administration. The gfs_grow command provides a -T (test) option that allows you to see the results of executing the command without actually expanding the file system. Using this command with the -v provides additional information. After running the gfs_grow command, you can run a df MountPoint command on the file system to check that the new space is now available in the file system. Examples In this example, the underlying logical volume for the file system file system on the /mnt/gfs directory is extended, and then the file system is expanded. [root@tng3-1 ~]# lvextend -L35G /dev/gfsvg/gfslv Extending logical volume gfslv to GB Logical volume gfslv successfully resized [root@tng3-1 ~]# gfs_grow /mnt/gfs FS: Mount Point: /mnt/gfs FS: Device: /dev/mapper/gfsvg-gfslv FS: Options: rw,hostdata=jid=0:id=196609:first=1 26

31 Chapter 4. Managing GFS FS: Size: DEV: Size: Preparing to write new FS information... Done. Complete Usage gfs_grow [Options] {MountPoint Device} [MountPoint Device] MountPoint Device Specifies the directory where the GFS file system is mounted. Specifies the device node of the file system. Table 4.3, GFS-specific Options Available While Expanding A File System describes the GFS-specific options that can be used while expanding a GFS file system. Table 4.3. GFS-specific Options Available While Expanding A File System Option Description -h Help. Displays a short usage message. -q Quiet. Turns down the verbosity level. -T Test. Do all calculations, but do not write any data to the disk and do not expand the file system. -V Displays command version information. -v Turns up the verbosity of messages Adding Journals to a File System The gfs_jadd command is used to add journals to a GFS file system after the device where the file system resides has been expanded. Running a gfs_jadd command on a GFS file system uses space between the current end of the file system and the end of the device where the file system resides. When the fill operation is completed, the journal index is updated. The gfs_jadd command must be run on mounted file system, but it only needs to be run on one node in the cluster. All the other nodes sense that the expansion has occurred. To verify that the changes were successful, use the gfs_jadd command with the -T (test) and -v (verbose) flags. Running the command with those flags displays the current state of the mounted GFS file system. Usage gfs_jadd -j Number MountPoint Number Specifies the number of new journals to be added. 27