Data ONTAP 8.2 Storage Management Guide For 7-Mode

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1 IBM System Storage N series Data ONTAP 8.2 Storage Management Guide For 7-Mode SC

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3 Table of Contents 3 Contents Preface About this guide Supported features Websites Getting information, help, and service Before you call Using the documentation Hardware service and support Firmware updates How to send your comments Data ONTAP storage architecture overview Managing disks using Data ONTAP How Data ONTAP reports disk types Storage connection types and topologies supported by Data ONTAP How disks can be combined for the SAS storage connection type How disks can be combined for the FC-AL storage connection type Methods of calculating aggregate and system capacity Disk speeds supported by Data ONTAP How drive checksum types affect aggregate and spare management Drive name formats Loop IDs for FC-AL connected disks Understanding RAID disk types How disk sanitization works Disk sanitization process When disk sanitization cannot be performed What happens if disk sanitization is interrupted How selective disk sanitization works Tips for creating and backing up aggregates containing data to be sanitized How Data ONTAP monitors disk performance and health What happens when Data ONTAP takes disks offline How Data ONTAP reduces disk failures using Rapid RAID Recovery... 32

4 4 Storage Management Guide How the maintenance center helps prevent drive errors How Data ONTAP uses continuous media scrubbing to prevent media errors Increasing storage availability by using ACP Enabling ACP How you use SSDs to increase storage performance How Data ONTAP manages SSD wear life Capability differences between SSDs and HDDs Guidelines and requirements for using multi-disk carrier storage shelves How Data ONTAP avoids RAID impact when a multi-disk carrier must be removed How to determine when it is safe to remove a multi-disk carrier Spare requirements for multi-disk carrier disks Shelf configuration requirements for multi-disk carrier storage shelves Aggregate requirements for disks in multi-disk carrier storage shelves Considerations for using disks from a multi-disk carrier storage shelf in an aggregate Adding disks to a storage system When you need to update the Disk Qualification Package Replacing disks that are currently being used in an aggregate Replacing a self-encrypting disk Converting a data disk to a hot spare Removing disks from a storage system Removing a failed disk Removing a hot spare disk Removing a data disk Using disk sanitization to remove data from disks Removing data from disks using selective disk sanitization Stopping disk sanitization How ownership for disks and array LUNs works Reasons to assign ownership of disks and array LUNs What it means for Data ONTAP to own an array LUN Why you might assign array LUN ownership after installation How disks and array LUNs become available for use How automatic ownership assignment works for disks What automatic ownership assignment does... 62

5 Table of Contents 5 When automatic ownership assignment is invoked Examples showing when Data ONTAP can use array LUNs Managing ownership for disks and array LUNs Guidelines for assigning ownership for disks Assigning ownership for unowned disks and array LUNs Removing ownership from a disk Configuring automatic ownership assignment of disks Modifying assignment of spare disks or array LUNs Verifying the existence of two paths to an array LUN Verifying the existence of two paths: storage show disk command Verifying the existence of two paths: storage array show-config command Verifying path failover for array LUNs Verifying path failover for array LUNs in a stand-alone system Verifying path failover for array LUNs in an HA pair Guidelines for assigning disks or array LUNs to SyncMirror pools How you use the wildcard character with the disk ownership commands Managing array LUNs using Data ONTAP Systems running Data ONTAP that can use array LUNs on storage arrays Array LUN name format Guidelines for adding storage to a storage system that uses array LUNs Checking the checksum type of spare array LUNs Changing the checksum type of an array LUN Prerequisites to reconfiguring an array LUN on the storage array Changing array LUN size or composition Removing one array LUN from use by Data ONTAP Preparing array LUNs before removing a system running Data ONTAP from service Commands to display information about your storage Commands to display drive and array LUN information Commands to display space information Commands to display storage subsystem information Enabling or disabling a host adapter Introduction to Storage Encryption What Storage Encryption is Purpose of the external key management server... 91

6 6 Storage Management Guide How Storage Encryption works Disk operations with SEDs Benefits of using Storage Encryption Data protection in case of disk loss or theft Data protection when returning disks to vendors Data protection when moving disks to end-of-life Data protection through emergency data shredding Limitations of Storage Encryption Managing Storage Encryption Displaying Storage Encryption disk information Displaying key management server information Verifying key management server links Adding key management servers Removing key management servers What happens when key management servers are not reachable during the boot process Changing the authentication key Retrieving authentication keys Deleting an authentication key SSL issues due to expired certificates Removing old SSL certificates before installing new ones Installing replacement SSL certificates on the storage system Returning SEDs to unprotected mode Destroying data on disks using Storage Encryption Sanitizing disks using Storage Encryption before return to vendor Setting the state of disks using Storage Encryption to end-of-life Emergency shredding of data on disks using Storage Encryption How Data ONTAP uses RAID to protect your data and data availability RAID protection levels for disks What RAID-DP protection is What RAID4 protection is RAID protection for array LUNs Protection provided by RAID and SyncMirror Understanding RAID disk types How RAID groups work

7 Table of Contents 7 How RAID groups are named About RAID group size Considerations for sizing RAID groups for drives Considerations for Data ONTAP RAID groups for array LUNs How Data ONTAP works with hot spare disks How many hot spares you should have What disks can be used as hot spares What a matching spare is What an appropriate hot spare is About degraded mode How low spare warnings can help you manage your spare drives How Data ONTAP handles a failed disk with a hot spare How Data ONTAP handles a failed disk that has no available hot spare Considerations for changing the timeout RAID option How RAID-level disk scrubs verify data integrity How you schedule automatic RAID-level scrubs How you run a manual RAID-level scrub Customizing the size of your RAID groups Controlling the impact of RAID operations on system performance Controlling the performance impact of RAID data reconstruction Controlling the performance impact of RAID-level scrubbing Controlling the performance impact of plex resynchronization Controlling the performance impact of mirror verification What aggregates are Introduction to 64-bit and 32-bit aggregate formats Best practices for expanding a 32-bit aggregate to 64-bit How unmirrored aggregates work How mirrored aggregates work What a Flash Pool aggregate is How Flash Pool aggregates work Requirements for using Flash Pool aggregates How Flash Pool aggregates and Flash Cache compare About read and write caching for Flash Pool aggregates How the available Flash Pool cache capacity is calculated Restrictions for using aggregates composed of SSDs How you can use disks with mixed speeds in the same aggregate

8 8 Storage Management Guide How to control disk selection from heterogeneous storage Rules for mixing HDD types in aggregates Rules for mixing drive types in Flash Pool aggregates How drive checksum types affect aggregate and spare management Rules for mixing storage in array LUN aggregates How the checksum type is determined for array LUN aggregates Understanding the root aggregate Managing aggregate Snapshot copies Considerations for increasing the aggregate Snapshot reserve Managing aggregates Creating an aggregate Creating a Flash Pool aggregate Determining and enabling volume write-caching eligibility Using the Automated Workflow Analyzer (AWA) feature to optimize Flash Pool cache size Changing the RAID type of RAID groups in a Flash Pool aggregate Increasing the size of an aggregate What happens when you add storage to an aggregate Forcibly adding disks to aggregates Expanding an aggregate to 64-bit without adding storage Taking an aggregate offline Bringing an aggregate online Putting an aggregate into restricted state Changing the RAID level of an aggregate Changing an aggregate's RAID level from RAID4 to RAID-DP Changing an aggregate's RAID level from RAID-DP to RAID Destroying an aggregate Restoring a destroyed aggregate Physically moving an aggregate composed of disks Moving an aggregate composed of array LUNs Using volumes How FlexVol volumes work Differences between 64-bit and 32-bit FlexVol volumes Interoperability between 64-bit and 32-bit FlexVol volumes How traditional volumes work How the volume language attribute affects data visibility and availability

9 Table of Contents 9 How file access protocols affect what language to use for your volumes How to manage duplicate volume names Volume states and status How security styles affect data access Improving client performance with traditional and lease oplocks How Data ONTAP can automatically provide more space for full FlexVol volumes Considerations for changing the maximum number of files allowed on a volume. 181 Cautions for increasing the maximum directory size for FlexVol volumes Understanding the root volume Recommendations for the root volume Special system files General volume operations Migrating from traditional volumes to FlexVol volumes Preparing your destination volume Migrating your data Completing the migration Putting a volume into restricted state Taking a volume offline Bringing a volume online Renaming a volume Destroying a volume Displaying file or inode usage Changing the maximum number of files allowed in a volume Changing the language for a volume Changing the root volume FlexVol volume operations Creating a FlexVol volume Resizing a FlexVol volume Displaying the containing aggregate for a FlexVol volume Traditional volume operations Creating a traditional volume Using FlexCache volumes to accelerate data access How FlexCache volumes serve read requests FlexCache hardware and software requirements Limitations of FlexCache volumes

10 10 Storage Management Guide Types of volumes you can use for FlexCache How the FlexCache Autogrow capability works How FlexCache volumes use space management How FlexCache volumes share space with other volumes Methods to view FlexCache statistics What happens when connectivity to the origin system is lost How the NFS export status of the origin volume affects FlexCache access How FlexCache caching works What a cached file contains How data changes affect FlexCache volumes How cache consistency is achieved What cache hits and misses are Typical FlexCache deployments WAN deployment LAN deployment Using FlexCache volumes to cache clustered Data ONTAP volumes About using LUNs in FlexCache volumes What FlexCache status messages mean How FlexCache volumes connect to their origin volume FlexCache volume operations Creating FlexCache volumes Displaying free space for FlexCache volumes Configuring the FlexCache Autogrow capability Flushing files from FlexCache volumes Displaying FlexCache client statistics Displaying FlexCache server statistics Displaying FlexCache status Using FlexClone volumes to create efficient copies of your FlexVol volumes Understanding FlexClone volumes FlexClone volumes and space guarantees How to identify shared Snapshot copies in FlexClone volumes FlexClone volumes and shared Snapshot copies How you use volume SnapMirror replication with FlexClone volumes Considerations for creating a FlexClone volume from a SnapMirror source or destination volume

11 Table of Contents 11 How splitting a FlexClone volume from its parent works FlexClone volumes and LUNs FlexClone volume operations Creating a FlexClone volume Splitting a FlexClone volume from its parent Determining the parent volume and base Snapshot copy for a FlexClone volume Determining the space used by a FlexClone volume Moving your volumes nondisruptively Ways to use volume move Requirements for performing a volume move How the setup phase of volume move works How the data copy phase of volume move works How the cutover phase of volume move works Performing the volume move operation Pausing the volume move operation Resuming the volume move operation Monitoring the volume move status Performing manual cutover of the volume move operation Canceling the volume move operation Using FlexClone files and FlexClone LUNs to create efficient copies of files and LUNs Benefits of FlexClone files and FlexClone LUNs How FlexClone files and FlexClone LUNs work Considerations for working with FlexClone files and FlexClone LUNs Creating a FlexClone file or FlexClone LUN Viewing the space savings due to FlexClone files and FlexClone LUNs Features supported with FlexClone files and FlexClone LUNs How deduplication works with FlexClone files and FlexClone LUNs How Snapshot copies work with FlexClone files and FlexClone LUNs How access control lists work with FlexClone files and FlexClone LUNs How vfiler units work with FlexClone files and FlexClone LUNs How quotas work with FlexClone files and FlexClone LUNs How FlexClone volumes work with FlexClone files and FlexClone LUNs How NDMP works with FlexClone files and FlexClone LUNs How synchronous SnapMirror works with FlexClone files and FlexClone LUNs. 250

12 12 Storage Management Guide How volume SnapMirror works with FlexClone files and FlexClone LUNs How qtree SnapMirror and SnapVault work with FlexClone files and FlexClone LUNs How volume move affects FlexClone files and FlexClone LUNs How volume copy works with FlexClone files and FlexClone LUNs How space reservation works with FlexClone files and FlexClone LUNs How an HA configuration works with FlexClone files and FlexClone LUNs Using deduplication and data compression to increase storage efficiency How to set up efficiency operations Configuring deduplication How deduplication works What deduplication metadata is Guidelines for using deduplication Enabling deduplication on a volume Disabling deduplication on a volume Configuring data compression How data compression works How data compression detects incompressible data and saves system resources Enabling data compression on a volume Disabling data compression on a volume Managing volume efficiency operations using schedules Modifying scheduling of efficiency operations Running efficiency operations manually Running efficiency operations depending on the amount of new data written Using checkpoints to resume efficiency operation Running efficiency operations manually on existing data Monitoring volume efficiency operations Viewing the status of efficiency operations on a FlexVol volume Viewing efficiency space savings on a FlexVol volume Stopping volume efficiency operations Information about removing space savings from a volume Deduplication interoperability with Data ONTAP features How fractional reserve works with deduplication

13 Table of Contents 13 How Snapshot copies work with deduplication How volume SnapMirror works with deduplication How qtree SnapMirror works with deduplication How SnapVault works with deduplication How tape backup works with deduplication How SnapRestore works with deduplication How MetroCluster configurations work with deduplication How OnCommand Unified Manager server works with deduplication How volume copy works with deduplication How deduplication works with data compression How FlexClone volumes work with deduplication How HA pairs work with deduplication How vfiler units work with deduplication How Data Motion for Volumes works with deduplication Data compression interoperability with Data ONTAP features How fractional reserve works with data compression How Snapshot copies work with data compression How volume SnapMirror works with data compression How qtree SnapMirror works with data compression How SnapVault works with data compression How tape backup works with data compression How SnapLock works with data compression How volume-based SnapRestore works with data compression How single file SnapRestore works with data compression How MetroCluster configurations work with data compression How volume copy works with data compression How aggregate copy works with data compression How deduplication works with data compression How FlexClone volumes work with data compression How FlexClone files work with data compression How HA pairs work with data compression How Performance Acceleration Module and Flash cache cards work with data compression How vfiler units work with data compression How Data Motion for Volumes works with data compression How Flash Pool aggregates work with data compression

14 14 Storage Management Guide How you use space management capabilities How volume guarantees work with FlexVol volumes Enabling guarantees for FlexVol volumes How the guarantee affects FlexVol volume space requirements How file and LUN reservations work Considerations for setting fractional reserve How Data ONTAP can automatically provide more space for full FlexVol volumes Selecting the first method to increase space for full FlexVol volumes Deleting Snapshot copies automatically How a FlexVol volume can automatically change its size Configuring a FlexVol volume to automatically change its size Requirements for enabling both autoshrink and automatic Snapshot copy deletion How the autoshrink functionality interacts with Snapshot copy deletion Considerations for using thin provisioning with FlexVol volumes How to determine space usage in a volume or aggregate How to determine space usage in an aggregate How you can determine and control a volume's space usage in the aggregate How you can determine and control space usage in a volume How Snapshot copies and Snapshot reserve use space in a volume When to use the df command and the space usage commands Methods to create space in a FlexVol volume Methods to create space in an aggregate About qtrees When to use qtrees How qtrees compare with FlexVol volumes Qtree name restrictions Managing qtrees Creating a qtree Displaying qtree status Displaying qtree access statistics Converting a directory to a qtree Converting a directory to a qtree using a Windows client Converting a directory to a qtree using a UNIX client

15 Table of Contents 15 Deleting a qtree Renaming a qtree About quotas Why you use quotas Overview of the quota process Understanding quota notifications Quota targets and types Special kinds of quotas How default quotas work How you use explicit quotas How derived quotas work How you use tracking quotas How quotas are applied How quotas work with users and groups How you specify UNIX users for quotas How you specify Windows users for quotas How default user and group quotas create derived quotas How quotas are applied to the root user How quotas work with special Windows groups How quotas are applied to users with multiple IDs How Data ONTAP determines user IDs in a mixed environment How quotas with multiple users work How you link UNIX and Windows names for quotas How quotas work with qtrees How tree quotas work How user and group quotas work with qtrees How default tree quotas on a volume create derived tree quotas How default user quotas on a volume affect quotas for the qtrees in that volume How qtree changes affect quotas How deleting a qtree affects tree quotas How renaming a qtree affects quotas How changing the security style of a qtree affects user quotas Differences among hard, soft, and threshold quotas How the quotas file works The syntax of quota entries

16 16 Storage Management Guide How Data ONTAP reads the quotas file What character encodings are supported by the quotas file Sample quotas file How quotas are activated When you can use resizing When a full quota reinitialization is required How quotas work with vfiler units How quota reports work What fields quota reports contain How quota report options affect quota reports How the ID field is displayed in quota reports How you can use the quota report to see what quotas are in effect Difference in space usage displayed by a quota report and a UNIX client How a quota report accounts for disk space and file usage How the ls command accounts for space usage How the df command accounts for file size How the du command accounts for space usage Difference between a quota report and the df command in accounting space usage of CIFS sparse files Examples of using quotas Managing quotas Activating quotas Reinitializing quotas Deactivating quotas Canceling quota initialization Resizing quotas Deleting quotas Deleting a quota by removing resource restrictions Deleting a quota by removing the quotas file entry Managing quota message logging Displaying a quota report Using the quota report to determine which quotas limit writes to a specific file Storage limits Copyright information Trademark information Index

17 17 Preface About this guide This document applies to IBM N series systems running Data ONTAP. If the term 7-Mode is used in the document, it refers to Data ONTAP operating in 7-Mode, which has the same features and functionality found in the prior Data ONTAP 7.1, 7.2, and 7.3 release families. Starting with Data ONTAP 8.2.1, the capability of using LUNs on a storage array, formerly identified as gateway functionality, has a new name Data ONTAP FlexArray Virtualization Software. In this document, the term gateway describes IBM N series storage systems prior to Data ONTAP that have been ordered with the FlexArray Virtualization Software functionality (formerly known as gateway functionality). Gateways support various types of storage, and they are used with third-party disk storage systems for example, disk storage systems from IBM, HP, Hitachi Data Systems, and EMC. In this case, disk storage for customer data and the RAID controller functionality is provided by the back-end disk storage system. A gateway might also be used with disk storage expansion units specifically designed for the IBM N series models. Although the gateway product name has been retired as of Data ONTAP 8.2.1, Data ONTAP can access LUNs on all the same storage arrays as before, with the same functionality that the gateway product provided. The term filer describes IBM N series storage systems that either contain internal disk storage or attach to disk storage expansion units specifically designed for the IBM N series storage systems. New filer storage systems released with Data ONTAP and later can support third-party disk storage systems if the appropriate license is installed. Supported features IBM System Storage N series storage systems are driven by NetApp Data ONTAP software. Some features described in the product software documentation are neither offered nor supported by IBM. Please contact your local IBM representative or reseller for further details. Information about supported features can also be found on the N series support website (accessed and navigated as described in Websites on page 18).

18 18 Storage Management Guide Websites IBM maintains pages on the World Wide Web where you can get the latest technical information and download device drivers and updates. The following web pages provide N series information: A listing of currently available N series products and features can be found at the following web page: The IBM System Storage N series support website requires users to register in order to obtain access to N series support content on the web. To understand how the N series support web content is organized and navigated, and to access the N series support website, refer to the following publicly accessible web page: This web page also provides links to AutoSupport information as well as other important N series product resources. IBM System Storage N series products attach to a variety of servers and operating systems. To determine the latest supported attachments, go to the IBM N series interoperability matrix at the following web page: For the latest N series hardware product documentation, including planning, installation and setup, and hardware monitoring, service and diagnostics, see the IBM N series Information Center at the following web page: publib.boulder.ibm.com/infocenter/nasinfo/nseries/index.jsp Getting information, help, and service If you need help, service, or technical assistance or just want more information about IBM products, you will find a wide variety of sources available from IBM to assist you. This section contains information about where to go for additional information about IBM and IBM products, what to do if you experience a problem with your IBM N series product, and whom to call for service, if it is necessary. Before you call Before you call, make sure you have taken these steps to try to solve the problem yourself: Check all cables to make sure they are connected. Check the power switches to make sure the system is turned on. Use the troubleshooting information in your system documentation and use the diagnostic tools that come with your system. Refer to the N series support website (accessed and navigated as described in Websites on page 18) for information on known problems and limitations.

19 Preface 19 Using the documentation The latest versions of N series software documentation, including Data ONTAP and other software products, are available on the N series support website (accessed and navigated as described in Websites on page 18). Current N series hardware product documentation is shipped with your hardware product in printed documents or as PDF files on a documentation CD. For the latest N series hardware product documentation PDFs, go to the N series support website. Hardware documentation, including planning, installation and setup, and hardware monitoring, service, and diagnostics, is also provided in an IBM N series Information Center at the following web page: publib.boulder.ibm.com/infocenter/nasinfo/nseries/index.jsp Hardware service and support You can receive hardware service through IBM Integrated Technology Services. Visit the following web page for support telephone numbers: Firmware updates IBM N series product firmware is embedded in Data ONTAP. As with all devices, ensure that you run the latest level of firmware. Any firmware updates are posted to the N series support website (accessed and navigated as described in Websites on page 18). Note: If you do not see new firmware updates on the N series support website, you are running the latest level of firmware. Verify that the latest level of firmware is installed on your machine before contacting IBM for technical support. How to send your comments Your feedback helps us to provide the most accurate and high-quality information. If you have comments or suggestions for improving this document, please send them by to starpubs@us.ibm.com. Be sure to include the following: Exact publication title

20 20 Storage Management Guide Publication form number (for example, GC ) Page, table, or illustration numbers A detailed description of any information that should be changed

21 21 Data ONTAP storage architecture overview Storage architecture refers to how Data ONTAP provides data storage resources to host or client systems and applications. Data ONTAP distinguishes between the physical layer of data storage resources and the logical layer. The physical layer includes drives, array LUNs, RAID groups, plexes, and aggregates. Note: A drive (or disk) is the basic unit of storage for storage systems that use Data ONTAP to access native disk shelves. An array LUN is the basic unit of storage that a storage array provides to a storage system that runs Data ONTAP. The logical layer includes the file systems volumes, qtrees, logical unit numbers (LUNs) and the directories and files that store data. Note: LUNs are storage target devices in iscsi and FC networks. Aggregates provide storage to volumes. Aggregates can be composed of either drives or array LUNs, but not both. Data ONTAP organizes the drives or array LUNs in an aggregate into one or more RAID groups. RAID groups are then collected into one or two plexes, depending on whether RAIDlevel mirroring (SyncMirror) is in use. Aggregates can have two formats: 32-bit and 64-bit. An aggregate's format affects its maximum size. Volumes are data containers. Clients can access the data in volumes through the access protocols supported by Data ONTAP. These protocols include Network File System (NFS), Common Internet File System (CIFS), HyperText Transfer Protocol (HTTP), Web-based Distributed Authoring and Versioning (WebDAV), Fibre Channel (FC), and Internet SCSI (iscsi). You can partition volumes and control resource usage using qtrees. You can create LUNs for use in a SAN environment, using the FC or iscsi access protocols. Volumes, qtrees, and LUNs contain directories and files. Related concepts Managing disks using Data ONTAP on page 22 Managing array LUNs using Data ONTAP on page 78 How Data ONTAP uses RAID to protect your data and data availability on page 111 What aggregates are on page 132 Using volumes on page 174 About qtrees on page 309

22 22 Storage Management Guide Managing disks using Data ONTAP Disks (sometimes also called drives) provide the basic unit of storage for storage systems running Data ONTAP that use native storage shelves. Understanding how Data ONTAP uses and classifies disks will help you manage your storage more effectively. How Data ONTAP reports disk types Data ONTAP associates a type with every disk. Data ONTAP reports some disk types differently than the industry standards; you should understand how Data ONTAP disk types map to industry standards to avoid confusion. When Data ONTAP documentation refers to a disk type, it is the type used by Data ONTAP unless otherwise specified. RAID disk types denote the role a specific disk plays for RAID. RAID disk types are not related to Data ONTAP disk types. For a specific configuration, the disk types supported depend on the storage system model, the shelf type, and the I/O modules installed in the system. For more information about the types of disks supported by your configuration, see the IBM System Storage N series Introduction and Planning Guide at the N series support website (accessed and navigated as described in Websites on page 18). The following tables show how Data ONTAP disk types map to industry standard disk types for the SAS and FC storage connection types, and for storage arrays: Table 1: SAS-connected storage Data ONTAP disk type Disk class Industry standard disk type Description BSAS Capacity SATA Bridged SAS-SATA disks with added hardware to enable them to be plugged into a SAS-connected storage shelf. FSAS Capacity NL-SAS Near Line SAS MSATA Capacity SATA SATA disk in multi-disk carrier storage shelf SAS Performance SAS Serial-Attached SCSI SSD Ultra-performance SSD Solid-state drives

23 Managing disks using Data ONTAP 23 Table 2: FC-connected storage Data ONTAP disk type Disk class ATA Capacity SATA FCAL Performance FC Industry standard disk type Description Table 3: Storage arrays Data ONTAP disk type Disk class Industry standard disk type Description LUN N/A LUN A logical storage device backed by storage arrays and used by Data ONTAP as a disk. These LUNs are referred to as array LUNs to distinguish them from the LUNs that Data ONTAP serves to clients. For information about best practices for working with different types of disks, see Technical Report 3437: Storage Subsystem Resiliency Guide. Note: This technical report contains information about NetApp products that IBM licenses and in some cases customizes. Technical reports might contain information about models and features that are not supported by IBM. Related concepts Rules for mixing HDD types in aggregates on page 142 Related information TR 3437: Storage Subsystem Resiliency Guide

24 24 Storage Management Guide Storage connection types and topologies supported by Data ONTAP Data ONTAP supports two storage connection types: Serial-Attached SCSI (SAS) and Fibre Channel (FC). The FC connection type supports three topologies: arbitrated loop, switched, and point-topoint. SAS, BSAS, FSAS, SSD, and MSATA disks use the SAS connection type. SAS-connected storage shelves are connected to the controller on a daisy chain called a stack. FC and ATA disks use the FC connection type with an arbitrated-loop topology (FC-AL). FC-connected storage shelves are connected to the controller on a loop. Array LUNs use the FC connection type, with either the point-to-point or switched topology. You cannot combine different connection types in the same loop or stack. However, for MetroCluster configurations, the FC and SAS connection types can be combined in a bridged connection, with FC on the controller side and SAS on the shelf side. The bridged connection can be used in either a direct-attached or switched topology. For more information, see Configuring a MetroCluster system with SAS disk shelves and FibreBridge 6500N bridges. How disks can be combined for the SAS storage connection type You can combine SAS-connected storage shelves containing performance disks and SAS-connected storage shelves containing capacity disks within the same stack, although this configuration is not recommended. Each SAS-connected storage shelf can contain only one class of disk (capacity, performance, or SSDs). The only exception to this rule is if the shelf is being used for a Flash Pool aggregate. In that case, for some SSD sizes and shelf models, you can combine SSDs and HDDs in the same shelf. For more information, see the IBM System Storage N series Introduction and Planning Guide. How disks can be combined for the FC-AL storage connection type You cannot combine storage shelves containing FC disks and storage shelves containing ATA disks in the same loop. Methods of calculating aggregate and system capacity You use the physical and usable capacity of the drives you employ in your storage systems to ensure that your storage architecture conforms to the overall system capacity limits and the size limits of your aggregates. To maintain compatibility across different brands of drives, Data ONTAP rounds down (right-sizes) the amount of space available for user data. In addition, the numerical base used to calculate capacity

25 Managing disks using Data ONTAP 25 (base 2 or base 10) also impacts sizing information. For these reasons, it is important to use the correct size measurement, depending on the task you want to accomplish: For calculating overall system capacity, you use the physical capacity of the drive, and count every drive that is owned by the storage system. For calculating how many drives you can put into an aggregate before you exceed its maximum size, you use the right-sized, or usable, capacity of all data drives in that aggregate. Parity, dparity, and cache drives are not counted against the maximum aggregate size. To see the physical and usable capacity for a specific drive, see the IBM System Storage N series Introduction and Planning Guide at the N series support website (accessed and navigated as described in Websites on page 18). Disk speeds supported by Data ONTAP For hard disk drives, which use rotating media, speed is measured in revolutions per minute (RPM). Faster drives provide more input/output operations per second (IOPS) and faster response time. It is best to use disks of the same speed in an aggregate. Data ONTAP supports the following rotational speeds for hard disk drives: Performance disks (SAS-connected) 10K RPM 15K RPM Capacity disks (SAS-connected) 7.2K RPM Performance disks (FC-connected) 10K RPM 15K RPM Capacity disks (FC-connected) 7.2K RPM Solid-state drives, or SSDs, are flash media-based devices and therefore the concept of rotational speed does not apply to them. For more information about which disks are supported with specific hardware configurations, see the IBM System Storage N series Introduction and Planning Guide at the N series support website (accessed and navigated as described in Websites on page 18). Related concepts How you can use disks with mixed speeds in the same aggregate on page 140 What aggregates are on page 132

26 26 Storage Management Guide How drive checksum types affect aggregate and spare management There are two checksum types available for drives used by Data ONTAP: BCS (block) and AZCS (zoned). Understanding how the checksum types differ and how they impact storage management enables you to manage your storage more effectively. Both checksum types provide the same resiliency capabilities. BCS optimizes for data access speed, and reserves the smallest amount of capacity for the checksum for drives with 520-byte sectors. AZCS provides enhanced storage utilization and capacity for drives with 512-byte sectors. You cannot change the checksum type of a drive. To determine the checksum type of a specific drive model, see the IBM System Storage N series Introduction and Planning Guide. Aggregates have a checksum type, which is determined by the checksum type of the drives or array LUNs that compose the aggregate. The following configuration rules apply to aggregates, drives, and checksums: Checksum types cannot be combined within RAID groups. This means that you must consider checksum type when you provide hot spare drives. When you add storage to an aggregate, if it has a different checksum type than the storage in the RAID group to which it would normally be added, Data ONTAP creates a new RAID group. An aggregate can have RAID groups of both checksum types. These aggregates have a checksum type of mixed. For mirrored aggregates, both plexes must have the same checksum type. Drives of a different checksum type cannot be used to replace a failed drive. You cannot change the checksum type of a drive. Drive name formats Each drive has a name that differentiates it from all other drives. Drive names have different formats, depending on the connection type (FC or SAS) and how the drive is attached. The following table shows the various formats for drive names, depending on how they are connected to the storage system. Note: For internal drives, the slot number is zero, and the internal port number depends on the system model.

27 Managing disks using Data ONTAP 27 Drive connection Drive name Example SAS, direct-attached <slot><port>.<shelfid>.<bay> The drive in shelf 2, bay 11, connected to onboard port 0a is named 0a The drive in shelf 6, bay 3, connected to an HBA in slot 1, port c, is named 1c.6.3. SAS, direct-attached in multi-disk carrier disk shelf <slot><port>.<shelfid>.<bay>l<carrierposition> Carrier position is 1 or 2. SAS, bridge-attached (FibreBridge, used for MetroCluster configurations) SAS, bridge-attached through a switch (FibreBridge, used for MetroCluster configurations) <slot><port>.<loopid>l<lun> <switch_name>:<switch_port>.<loopid>l<lun> The drive with LUN 2 behind the bridge connected to port a in slot 3, loop ID 125, is named 3a.125L2. The drive with LUN 5 behind the bridge connected to port 2 of switch brcd44, loop ID 126, is named brcd44:2.126l5. FC, direct-attached <slot><port>.<loopid> The drive with loop ID 19 (bay 3 of shelf 1) connected to onboard port 0a is named 0a.19. The drive with loop ID 34 connected to an HBA in slot 8, port c is named 8c. 34.

28 28 Storage Management Guide Drive connection Drive name Example FC, switch-attached <switch_name>.<switch_port>.<loopid> The drive with loop ID 51 connected to port 3 of switch SW7 is named SW For information about determining the LUN for drives using the FibreBridge connection architecture, see Configuring a MetroCluster system with SAS disk shelves and FibreBridge 6500N bridges. Loop IDs for FC-AL connected disks For disks connected using Fibre Channel-Arbitrated Loop (FC-AL or FC), the loop ID is an integer between 16 and 126. The loop ID identifies the disk within its loop, and is included in the disk name, which identifies the disk uniquely for the entire system. The loop ID corresponds to the storage shelf number and the bay in which the disk is installed. The lowest loop ID is always in the far right bay of the first storage shelf. The next higher loop ID is in the next bay to the left, and so on. You can view the device map for your storage shelves by using the fcadmin device_map command. For more information about the loop ID map for your storage shelf, see the hardware guide for the storage shelf. Understanding RAID disk types Data ONTAP classifies disks as one of four types for RAID: data, hot spare, parity, or dparity. The RAID disk type is determined by how RAID is using a disk; it is different from the Data ONTAP disk type. Data disk Spare disk Parity disk Holds data stored on behalf of clients within RAID groups (and any data generated about the state of the storage system as a result of a malfunction). Does not hold usable data, but is available to be added to a RAID group in an aggregate. Any functioning disk that is not assigned to an aggregate but is assigned to a system functions as a hot spare disk. Stores row parity information that is used for data reconstruction when a single disk drive fails within the RAID group. dparity disk Stores diagonal parity information that is used for data reconstruction when two disk drives fail within the RAID group, if RAID-DP is enabled.

29 Managing disks using Data ONTAP 29 How disk sanitization works Disk sanitization is the process of physically obliterating data by overwriting disks or SSDs with specified byte patterns or random data so that recovery of the original data becomes impossible. You use the sanitization process to ensure that no one can recover the data on the disks. Related tasks Using disk sanitization to remove data from disks on page 49 Destroying data on disks using Storage Encryption on page 107 Disk sanitization process Understanding the basics of the disk sanitization process helps you understand what to anticipate during the sanitization process and after it is complete. The disk sanitization process uses three successive default or user-specified byte overwrite patterns for up to seven cycles per operation. The random overwrite pattern is repeated for each cycle. Depending on the disk capacity, the patterns, and the number of cycles, the process can take several hours. Sanitization runs in the background. You can start, stop, and display the status of the sanitization process. The sanitization process contains two phases: 1. Formatting phase The operation performed for the formatting phase depends on the class of disk being sanitized, as shown in the following table: Disk class Capacity HDDs Performance HDDs SSDs Formatting phase Skipped SCSI format operation SCSI sanitize operation 2. Pattern overwrite phase The specified overwrite patterns are repeated for the specified number of cycles. When the sanitization process is complete, the specified disks are in a sanitized state. They are not returned to spare status automatically. You must return the sanitized disks to the spare pool before the newly sanitized disks are available to be added to another aggregate.

30 30 Storage Management Guide When disk sanitization cannot be performed Disk sanitization is not supported for all disk types. In addition, there are times when disk sanitization cannot be performed. You should be aware of the following facts about the disk sanitization process: It is not supported on all SSD part numbers. For information about which SSD part numbers support disk sanitization, see the IBM System Storage N series Introduction and Planning Guide at the N series support website (accessed and navigated as described in Websites on page 18). It is not supported in takeover mode for systems in an HA pair. It cannot be performed on disks that were failed due to readability or writability problems. It cannot be performed on disks that belong to an SEC 17a-4-compliant SnapLock volume until the expiration periods on all files have expired--that is, all of the files have reached their retention dates. It does not perform its formatting phase on ATA drives. If you are using the random pattern, it cannot be performed on more than 100 disks at one time. It is not supported on array LUNs. If you sanitize both SES disks in the same ESH shelf at the same time, you see errors on the console about access to that shelf, and shelf warnings are not reported for the duration of the sanitization. However, data access to that shelf is not interrupted. You can perform disk sanitization on disks using Storage Encryption. However, there are other methods to obliterate data on disks using Storage Encryption that are faster and do not require an operational storage system. What happens if disk sanitization is interrupted Disk sanitization is a long-running operation. If disk sanitization is interrupted by user intervention or an unexpected event such as a power outage, Data ONTAP takes action to return the disks that were being sanitized to a known state, but you must also take action before the sanitization process can finish. If the sanitization process is interrupted by power failure, system panic, or manual intervention, the sanitization process must be repeated from the beginning. The disk is not designated as sanitized. If the formatting phase of disk sanitization is interrupted, Data ONTAP must recover any disks that were corrupted by the interruption. After a system reboot and once every hour, Data ONTAP checks for any sanitization target disk that did not complete the formatting phase of its sanitization. If any such disks are found, Data ONTAP recovers them. The recovery method depends on the type of the disk. After a disk is recovered, you can rerun the sanitization process on that disk; for HDDs, you can use the -s option to specify that the formatting phase is not repeated again.

31 Managing disks using Data ONTAP 31 How selective disk sanitization works Selective disk sanitization consists of physically obliterating data in specified files or volumes while preserving all other data located on the affected aggregate for continued user access. Because a file can be stored on multiple disks, there are three parts to the process. To selectively sanitize data contained in an aggregate, you must carry out three general tasks: 1. Delete the files, directories or volumes that contain the data you want to sanitize from the aggregate that contains them. 2. Migrate the data that you want to preserve to a new set of disks in a destination aggregate on the same storage system. You can migrate data using the ndmpcopy command or qtree SnapMirror. 3. Destroy the original aggregate and sanitize all the disks that were RAID group members in that aggregate. Related tasks Removing data from disks using selective disk sanitization on page 52 Tips for creating and backing up aggregates containing data to be sanitized If you are creating or backing up aggregates to contain data that might need to be sanitized, following some simple guidelines will reduce the time it takes to sanitize your data. Make sure your aggregates containing sensitive data are not larger than they need to be. If they are larger than needed, sanitization requires more time, disk space, and bandwidth. When you back up aggregates containing sensitive data, avoid backing them up to aggregates that also contain large amounts of nonsensitive data. This reduces the resources required to move nonsensitive data before sanitizing sensitive data. How Data ONTAP monitors disk performance and health Data ONTAP continually monitors disks to assess their performance and health. When Data ONTAP encounters certain errors or behaviors from a disk, it takes the disk offline temporarily or takes the disk out of service to run further tests. What happens when Data ONTAP takes disks offline Data ONTAP temporarily stops I/O activity to a disk and takes a disk offline when Data ONTAP is updating disk firmware in background mode or when disks become non-responsive. While the disk is offline, Data ONTAP performs a quick check on it to reduce the likelihood of forced disk failures. A disk can be taken offline only if its containing RAID group is in a normal state and the plex or aggregate is not offline.