Authors. Punita. Rajeswari Ayyaswamy. Lokesh Thutaram. Sanjeev Dambal. September, 2017

Transcription

1 Online Capacity Expansion (OCE) and RAID-Level Migration (RLM) of Virtual Drives by using PERC 9 and PERC 10 on the 14 th Generation (14G) Dell EMC PowerEdge servers This technical white paper describes the advantages of using RAID OCE and RLM on Dell EMC PowerEdge servers to increase capacity and change RAID level of an existing VD without having to restart the system. September, 2017 Authors Punita Rajeswari Ayyaswamy Lokesh Thutaram Sanjeev Dambal

2 The information in this publication is provided as is. Dell Inc. makes no representations or warranties of any kind with respect to the information in this publication, and specifically disclaims implied warranties of merchantability or fitness for a particular purpose. Use, copying, and distribution of any software described in this publication requires an applicable software license. Copyright 2017 Dell Inc. or its subsidiaries. All Rights Reserved. Dell, EMC, and other trademarks are trademarks of Dell Inc. or its subsidiaries. Other trademarks may be the property of their respective owners. Published in the USA [07/17] [Technical White Paper] Dell EMC believes the information in this document is accurate as of its publication date. The information is subject to change without notice. (14G) Dell EMC PowerEdge server 2

3 CONTENTS EXECUTIVE SUMMARY... 4 INTRODUCTION... 5 WHY OCE AND RLM ARE IMPORTANT VALUE ADDED FEATURES?... 5 Online Capacity Expansion (OCE)... 6 RAID Level Migration (RLM)... 6 OCE and RLM use cases... 7 Use case Use Case Use Case Use case ERROR CODES TROUBLESHOOTING (14G) Dell EMC PowerEdge server 3

4 EXECUTIVE SUMMARY The customers of Dell EMC PowerEdge servers typically create Virtual Drives (VDs) and then install applications and/or operating systems (OSs), on these VDs. Over time it is possible that these VDs are not able to meet the increasing storage capacity and/or redundancy requirements of an application. With earlier generations of idrac, customers required to have a system down-time to migrate these applications to the new VDs that have higher capacity and different RAID level to meet the expectations of the application. This technical white paper describes a method to increase the capacity of an existing VD while it is Online (no system down-time). It also enables customers to change the drive failure tolerance (which is decided by the RAID level of a VD) of an Online VD by changing its RAID level. (14G) Dell EMC PowerEdge server 4

5 Introduction The following diagram shows the evolution of Storage Configuration features of the DELL EMC servers. 12G - Host reboot required for all Storage Configurations 14G - Host reboot NOT required for additional Storage Configturation Features to provide parity with OMSS 13G - Host reboot NOT required for most of the key Storage Configuration features Figure 1 Storage Configuration Feature evolution on DELL EMC servers The 12th generation platforms of Dell EMC storage configurations, required a reboot to apply the configuration changes made using the idrac interfaces. This not only took more time to apply the configuration but also required exiting applications running on the host. Dell EMC13 th generation servers introduced real-time configuration for key storage operations that allow an agent-free, no-reboot method for configuring storage. 13G servers eliminate the need of either an OS agent (Open Management Storage Services, part of the OpenManage Server Assistant or OMSA) or a server reboot into the controller s firmware interface for most of the storage configuration, but still there was a gap when compared with storage configuration provided by OMSS. Dell EMC 14 th generation servers fills this gap by supporting additional storage configuration that require no host reboot. These features were so far available to idrac8 customers by using OS agent (Open Management Storage Services, part of the OpenManage Server Assistant or OMSA) only. The two key storage configuration features for a Virtual Drive are Online Capacity Expansion (OCE) and RAID-Level Migration (RLM). These features are discussed in detail in this technical whitepaper. For more information about the RAID commands to perform each of these functions, refer to the idrac homepage on the Dell TechCenter, and then search for the idrac interface you want to use to perform the specific RAID action. Why OCE and RLM are important value added features? The properties of a VD, such as its number of drives, drive failure tolerance (RAID level), and VD capacity (size), are defined at the time of VD creation. idrac9 Storage configuration now allows you to increase the VD capacity online and change its RAID levels while the VD is Online. These configuration changes can be accomplished with or without adding new drives. (14G) Dell EMC PowerEdge server 5

6 Online Capacity Expansion (OCE) Online Capacity Expansion allows you to increase the storage capacity of a VD while the system remains online. The controller redistributes the data on the array, by making new space available at the end of the RAID array. All VD RAID levels (except RAID 50 and RAID 60) are currently supported. OCE is achieved by using the unused space on a VD disk group that is available after the ending LBA of VDs. The smallest disk drive in the VD group determines the possible expansion size of the VD. Additional drives can also be added in cases where no free space is available on existing disk group of the VD. Online Capacity Expansion (OCE) can be done in two ways. If there is a single VD in a disk group and free space is available at the end of the VD, the VD s capacity can be expanded within that free space. If a VD is created and it does not use the maximum size of the disk group and no additional VDs have been created in that disk group, then free space is available and the VD can be expanded to use that free space. A VD s capacity can also be expanded by performing an OCE operation by adding more physical drives. RAID Level Migration (RLM) RAID Level Migration (RLM) refers to changing a VD s RAID level. An option to increase the VD size is also supported as part of this feature. Therefore, this feature provides ability to change the size of VD along with migrating RAID level of a VD. When a VD is migrated to a different RAID Level, the user data on it is redistributed to the format of the new configuration. The data redistribution process is a background task and its progress can be monitored by the user. The table describes possible reconfigurable VD layouts while reconfiguring (RLM) a VD with and without addition of drives. Source VD Layout Possible target VD Layout with Disk Add R1 R0 (Single disk) R0 R5/R6 NA R1 R0/R5/R6 R0 R5 R0/R6 R0 R6 R0/R5 R0/R5 Possible target VD Layout without disk addition Disk group doesn t have free space NA (14G) Dell EMC PowerEdge server 6

7 OCE and RLM use cases This section illustrates use cases with examples where user can go for OCE and RLM. They can choose to change the drive failure tolerance from one drive failure (in RAID 5) to two drive failure (RAID6) by migrating from RAID 5 to RAID6 (Table provides valid RLMs possible). Use case 1 I have the OS on a RAID5 VD with 3 drives of GB each. If I do not want to change the redundancy of the VD and already disk space on the VDs are in use, then two new drives can be added and the capacity of new VD size will change to 1200 GB. Solution: Use idrac interface to do online capacity expansion by adding two new compatible drives. GUI example: 1. From the VD drop-down menu, select Edit Disk Capacity. 7

8 This page displays the disk space usage of drives in VD, and with existing configuration, there is no available space on drives. 2. Click Add Physical Disk. 3. From the list of physical drives displayed, select the drive that you want to add and click Add Disk.. 8

9 In the left pane, the total number of drives, available space on each drive, and the new VD size is displayed based on the drive added. This configuration will be applied on PERC after a job is created and reconfiguration is completed. Example RACADM command Syntax for OCE with drive addition: racadm>> storage capacityexpansion:disk.virtual.1:raid.slot pdkey:disk.bay.13:enclosure.external.0-0:raid.slot.2-1 racadm storage capacityexpansion:disk.virtual.1:raid.slot pdkey:disk.bay.13:enclosure.external.0-0:raid.slot.2-1 STOR094 : The storage configuration operation is successfully completed and the change is in pending state. To apply the configuration operation immediately, create a configuration job using the --realtime option. To apply the configuration after restarting the server, create a configuration job using the -r option. To create the necessary real-time and restart jobs, run the jobqueue command. For more information about jobqueue command, run the 'racadm help jobqueue' command. racadm>>jobqueue create RAID.Slot.2-1 -s TIME_NOW --realtime racadm jobqueue create RAID.Slot.2-1 -s TIME_NOW --realtime RAC1024: Successfully scheduled a job. Verify the job status using "racadm jobqueue view -i JID_xxxxx" command. Commit JID = JID_

10 Use Case 2 I have RAID5 VDs of size 600 GB 3 drives of 2 TB each. Of this, 1700 GB is unused on each drive. This VD was used for I/O operation and now VD size needs to be increased to use full drive usage. Solution: Use the idrac GUI to perform an OCE within an array. GUI example: 1. From the VD drop-down menu, select Edit Disk Capacity. 2. Select new capacity of the VD. In this case, entering maximum expansion that is possible. 10

11 Example RACADM command syntax: racadm>>storage capacityexpansion:disk.virtual.1:raid.slot.2-1 -size 371.5g - pdkey:disk.bay.13:enclosure.external.0-0:raid.slot.2-1 racadm storage capacityexpansion:disk.virtual.1:raid.slot.2-1 -size 371.5g - pdkey:disk.bay.13:enclosure.external.0-0:raid.slot.2-1 STOR094 : The storage configuration operation is successfully completed and the change is in pending state. To apply the configuration operation immediately, create a configuration job using the --realtime option. To apply the configuration after restarting the server, create a configuration job using the -r option. To create the necessary real-time and restart jobs, run the jobqueue command. For more information about jobqueue command, run the 'racadm help jobqueue' command. Use Case 3 I have a VD with RAID level 5 which is capable of one drive failure. Now, this VD is used to save more critical data and needs tolerance up to two drive failure which is provided by RAID6. Solution: Use the idrac interface to do RLM by adding one compatible drive. Example: On the idrac9 GUI: 1. From the VD drop-down menu, select RAID Level Migration. 11

12 2. From the New RAID Level drop-down menu, select the new RAID level you want to migrate to. RAID level will be listed based on compatible drive available for addition. 3. In the working pane, click Add Physical Disk to add new drives, and then click Add Disk. 12

13 A list of drives and new VD size calculated after new drive addition is displayed. This will be new VD configuration (number of drives and VD size) after job will be completed. Example of using WS-Man: C:\OMSS_Parity>winrm i RAIDLevelMigration DCIM_ComputerSystem+CreationClassName=DCIM_RAIDService+Syste mname=dcim:computersystem+name=dcim:raidservice -u:root - p:calvin -r: - SkipCNcheck - SkipCAcheck -encoding:utf-8 ";NewRaidLevel="128";PDArray=" Disk.Bay.13:Enclosure.External.0-0:RAID.Slot.2-1"} RAIDLevelMigration_OUTPUT RebootRequired = OPTIONAL ReturnValue = 0 Example of RACADM command syntax: racadm>>storage raidlevelmigration:disk.virtual.1:raid.slot.2-1 -new_rl r6 - pdkey:disk.bay.13:enclosure.external.0-0:raid.slot.2-1 racadm storage raidlevelmigration:disk.virtual.1:raid.slot.2-1 -new_rl r6 - pdkey:disk.bay.13:enclosure.external.0-0:raid.slot.2-1 STOR094 : The storage configuration operation is successfully completed and the change is in pending state. To apply the configuration operation immediately, create a configuration job using the --realtime option. To apply the configuration after restarting the server, create a configuration job using the -r option. 13

14 To create the necessary real-time and restart jobs, run the jobqueue command. For more information about jobqueue command, run the 'racadm help jobqueue' command. Use case 4 I have hot data on a RAID1 VD, which is currently used for I/O operation. This data changes after some time. Now, customers want to migrate to RAID5 by adding another drive. Solution: Use the idrac GUI to perform RAID-level migration by adding a new compatible drive. GUI example: 1. From the VD drop-down menu, select Raid Level Migration. 14

15 2. From the New RAID Level drop-down menu, select the new RAID level you want to migrate to. RAID level is listed based on compatible drive available for addition. 4. Click Add Physical Disk. 5. From the list of PDs displayed, select the drive that you want to add, and click Add Disk 15

16 A list of drives and new VD size is the addition of a new drive is displayed. This is the new configuration (number of drives and VD size) of VD after the job is successfully run. 16

17 Error codes The Event and Error messages displayed during online capacity expansion or failure of RLM. These messages are split into: Message (M): Displays the actual issue with possible causes. Indicated in blue in this section. Recommended Response Action (RRA): Lists the possible remedial actions you can perform to resolve the issue. STOR313: Unable to run the command to reconfigure the Virtual Disk because the storage controller does not support reconfiguration operations. Make sure of the following and retry the operation. The latest version of Lifecycle Controller firmware is installed. The storage controller supports reconfiguration process. For information about the supported storage controller versions, see the Lifecycle Controller User's Guide available on the support site. STOR314: Unable to start the reconfiguration operation on a Virtual Disk because a reconfiguration request for that Virtual Disk already exists. There are two possible response actions. Commit and execute the pending reconfiguration operation. After completion, retry the new Reconfiguration operation. Cancel the pending Reconfiguration operation and then retry the new reconfiguration operation. STOR315: Unable to perform the reconfiguration operation because the storage controller does not support reconfiguring a Virtual Disk that has more than one span. Make sure that the VD has a single span and retry the reconfiguration operation. For information about the RAID levels that have a single span, see the Lifecycle Controller User's Guide available at the support site. STOR316: Unable to perform the reconfiguration operation because the storage controller does not support reconfiguration of a Virtual Disk that is part of a disk group that has multiple Virtual Disks. Make sure that the physical disk group has a single Virtual Disk and retry the reconfiguration operation. 17

18 STOR317: Unable to perform the reconfiguration operation because the number of physical disks specified in the disk group is not as per the permitted range. Enter the correct number of physical disks for the reconfiguration operation and retry the operation. The number of physical disks in a disk group must be within the disk group's permissible range. For information about the minimum and maximum possible physical disks in a disk group, see the Lifecycle Controller User's Guide available at the support site. STOR318: Unable to perform the reconfiguration operation because the Virtual Disk size specified is invalid. Make sure that the Virtual Disk size specified for the reconfiguration operation is less than or equal to the maximum possible value. For information about the maximum possible value, see the Lifecycle Controller User's Guide available at the support site. STOR319: Unable to perform the operation because a reconfiguration operation is already in progress for the Virtual Disk. Wait for the current virtual disk (VD) configuration operation to complete and then retry operation. A configuration operation that is already in progress cannot be cancelled. STOR320: Unable to start the reconfiguration operation because the requested reconfiguration operation is invalid. There are two Reconfiguration operations possible on a Virtual Disk. Online Expansion of the storage capacity RAID level migration Only one of the above two operations can be specified in a Reconfiguration operation. Make sure that only one of the above two operation types is requested and retry the operation. 18

19 Troubleshooting This section explains possible reasons for behavior seen while reconfiguring. Any type of drive migration when the reconfiguration process is in progress (on the drives associated with VD) will cause reconfiguration to fail. Capacity Expansion allows you to specify the final VD size. Internally, final VD size is conveyed to PERC in percentage (this percentage is the space user would like to use from empty space left in the array for the LD to expand). Because of this percentage logic final VD size after reconfiguration completes may be different from what user provided for scenario where user is not giving maximum VD size possible as the final VD size (percentage turns out to be less than 100%). User will not see difference in this entered VD size and final VD size after reconfiguration if maximum possible VD size is entered by user. Reconfiguration impacts performance until the reconfiguration operation is in progress. To perform the OCE, you must have the System Control privilege. idrac will log a message into Lifecycle Log every time an OCE operation is performed. The OCE operation can only be performed on Disk Groups that have a single VD. If the copy-back operation is running on physical drives, the scheduled OCE or RLM job will fail on the associated VDs. RLM feature shall not be available when the Disk Group has more than one VD. The controller changes the write cache policy of all VDs undergoing a RLM to write through until the RLM is complete. 19