EMC CLARiiON LUN Shrinking with Microsoft Exchange 2007

Transcription

1 EMC CLARiiON LUN Shrinking with Microsoft Exchange 2007 Applied Technology Abstract This white paper discusses the EMC CLARiiON LUN shrinking feature in detail. It captures the business benefits and advantages of LUN shrinking by exploring the possibilities of integrating this feature in a typical Microsoft Exchange production environment. July 2010

2 Copyright 2010 EMC Corporation. All rights reserved. EMC believes the information in this publication is accurate as of its publication date. The information is subject to change without notice. THE INFORMATION IN THIS PUBLICATION IS PROVIDED AS IS. EMC CORPORATION 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 EMC software described in this publication requires an applicable software license. For the most up-to-date listing of EMC product names, see EMC Corporation Trademarks on EMC.com All other trademarks used herein are the property of their respective owners. Part Number: h8009 Applied Technology 2

3 Table of Contents Executive summary... 4 Introduction... 4 Audience... 4 Terminology... 4 Overview of LUN shrinking... 5 Host-side shrinking process... 5 Array-side shrinking process... 7 Additional considerations for LUN shrinking LUN shrinking with Microsoft Exchange Conclusion References Applied Technology 3

4 Executive summary This white paper discusses the advantages of using the EMC CLARiiON FLARE release 29 feature called LUN shrinking within a typical Microsoft Exchange production environment. This paper discusses the requirements and important considerations of LUN shrinking and explains the business benefits achieved by using this feature to increase the performance and usability of CLARiiON with Microsoft Exchange. LUN shrinking provides a significant advantage to storage provisioning by allowing the space in the storage array to be reused if it is no longer required by the application that was originally using it. LUN shrinking benefits organizations by creating higher storage utilization by reclaiming unused storage space. Secondly, LUN shrinking helps in green storage initiatives by minimizing the need for additional storage, hence saving cost and power. In the past, CLARiiON did not have a native solution to shrink the LUNs associated with Windows 2008 Disk Management. As a result, even after Windows OS level shrinking, the storage space on the array was still allocated. LUN shrinking is a CLARiiON feature introduced in FLARE release 29. This feature targets the unused space in the LUN, reduces the size of the LUN, and thus improves the storage utilization. Introduction This white paper gives information about the different aspects of LUN shrinking. The paper is designed to equip the reader with the necessary understanding to maximize the CLARiiON storage environment in a cost-effective way before seeking additional storage arrays. This paper gives a scenario of Microsoft Exchange 2007 using a CLARiiON CX4-480 with LUN shrinking to simulate a production environment. The purpose is to understand the impact and benefits of LUN shrinking in a Microsoft Exchange environment. This white paper explores the LUN shrinking feature and covers the following topics: The importance of LUN shrinking The benefits of shrinking a LUN (from a user perspective) The impact of the LUN shrink operation on the back-end storage objects A case study of shrinking the LUNs associated with Microsoft Exchange 2007 The EMC CLARiiON Storage System Fundamentals for Performance and Availability Applied Best Practices white paper provides specific information on FLARE, CLARiiON provisioning, LUNs, and RAID groups. Audience This white paper is targeted at customers, including storage architects, administrators, and others who may be involved in evaluating, acquiring, managing, operating, or designing an EMC networked storage environment. Terminology This section provides a brief description of the common terms used in this paper. LUN: A logical unit whose storage capacity is set at the time of creation. A LUN is created from a RAID group. LUN shrinking: A feature that is used to reduce the LUN size and increase the available disk space. Windows Server 2008: The most recent release of the Microsoft Windows Server operating system that includes a volume shrink feature, which allows users to reduce the size of a file system (volume and partition) and the underlying storage (LUN). Applied Technology 4

5 Virtual Disk Service (VDS) Provider: A VDS Provider that is used by Windows Server 2008 VDS to perform hardware provisioning and management operations. Thin Pool: A user-defined object that reserves and groups disks together for use by the Thin Provisioning feature. There may be 0 or more Thin Pools on a system. A disk can be a member of only one Thin Pool at a time. Disks that are members of a Thin Pool cannot be part of a RAID group. Thin LUN (TLU): A LUN that can grow storage capacity by using a shared pool of storage (Thin Pool), when required. EMC Solutions Enabler: A set of application programming interface (API) libraries that provide an interface between the software applications and the heterogeneous hardware and software infrastructure within a storage environment. Overview of LUN shrinking In the past, third-party tools such as Partition Magic were used to manage Windows-based disk partitions. The third-party tools required an external boot process to Microsoft operating systems from bootable CDs. These tools allowed disk reformatting and partition extension and reduction. Unlike previous Microsoft operating systems, Windows Vista and Windows Server 2008 allow an easy, out-of-the-box method to shrink partitions. The shrink feature in Disk Management is used to free up unused disk space to create another partition from the saved space. This feature functions in a similar way for both normal and dynamic disks. It enables administrators to manage Windows storage requirements, which is one of the more challenging administration areas. However, before FLARE release 29, even if the drive space was reduced from the host side, the array-side space allocation was not altered. This created a need for an array-side LUN shrinking feature. The following steps are involved in the LUN shrinking process when the storage is provisioned to a Windows system using storage arrays like CLARiiON. 1. Shrinking the drive space on the host side using the Windows Server 2008 Disk Management console. 2. Shrinking or destroying the metaluns or FLARE LUNs on the array side using the LUN shrinking feature. Host-side shrinking process Prior to Microsoft Windows Server 2008 and Microsoft Windows Vista, the server-side disk partitions were shrunk using third-party applications and the diskpart command line tool. But now this can be done in the Disk Management console within Windows Server 2008 Server Manager. During the shrinking operation, the data that is spread across the volume is moved so that it uses contiguous space at the beginning of the disk partition. This allows the unallocated space from the end of the disk partition to be freed up. Applied Technology 5

6 The first step in LUN shrinking is to perform a user-level volume shrink operation on Windows Server 2008 Disk Management. The following procedure explains this process. 1. In the Disk Management console, right-click the disk and select Shrink Volume. The Shrink dialog box appears. Figure 1 Disk Management 2. The available amount of free space in MB is displayed. Type the appropriate size lower than the available size and click Shrink. The disk partition shrinks to the required size. Figure 2 Shrink After the volume shrinks, the size of the drive reduces from the Disk Management console. But the unallocated space can be seen from the console because it is not removed from the array side. Figure 3 Drive size after shrinking At this point, the host-side activity is completed and the LUN size must be reduced on the array side using array features. Applied Technology 6

7 Array-side shrinking process After the volume size is reduced on the host, the Microsoft Windows Server 2008 diskraid command is used to shrink the CLARiiON LUN. This command in turn uses the VDS Provider to shrink the CLARiiON LUNs. Note: EMC VDS Provider Release Notes provides more information on the CLARiiON VDS Provider. CLARiiON LUN shrinking using the diskraid command and VDS Provider The steps to perform the array-side shrink process are: 1. On the Windows host, run the diskraid command from the command prompt. Figure 4 diskraid command 2. List the providers using the list providers command. Figure 5 list providers command 3. Select the required provider (FC or iscsi) based on the host and the array connectivity by using the select provider X command. Figure 6 select provider command 4. List the storage subsystems by using the list subsystems command. Figure 7 list subsystem command 5. Select the required subsystem by using the select subsys x command. Figure 8 select subsystem command Applied Technology 7

8 Note: The subsystem is displayed twice when listed because the array supports both FC and iscsi connectivity. To use the right connectivity to an array, use the detail provider command after selecting the subsystem. In the output, if the name of the provider is EMC VDS Hardware Provider, then FC connectivity is used to interact with the array. If iscsi connectivity is used, select the other instance. 6. List all the existing LUNs by using the list luns command. Figure 9 list luns command 7. Select the LUN corresponding to the device number to execute the shrink operation by using the select lun x command. Figure 10 select lun command Note: The LUN number on the array side and the host side may be different. The LUN number for the device may vary for every diskraid session. The device number must match the disk number displayed in the console. Select the LUN for which the device number matches the disk number. 8. Shrink the selected LUN by using the shrink lun size Y command, where Y is the size to be shrunk. Figure 11 shrink lun command 9. Verify the new size of the LUN by observing the LUN size using the list LUN command. 10. Verify the new LUN size on the array. For this, navigate to C:\Program Files\EMC\SYMCLI\bin and type in the following command: naviseccli h ipaddr getlun LUNnumber capacity 11. The LUN size after shrinking is visible in the Disk Management console. Figure 12 Before shrinking Applied Technology 8

9 Figure 13 After shrinking Shrinking metaluns MetaLUNs are made by joining a base FLARE LUN to one or more component FLARE LUNs. The component FLARE LUNs can be a part of the same RAID group or different RAID groups. The LUNs can be concatenated or striped together to create a metalun. The shrinking behavior is different in striped and concatenated metalun components. Striped metalun In a striped metalun, the component LUNs are striped together in groups with a single operation. All the base LUN data is equally distributed by striping across all LUNs. Striped metaluns improve the performance as well as protection. CLARiiON writes to all LUNs in the metalun at the same time. The workload of the application is spread out across the backend of the CLARiiON, thereby increasing the speed. Figure 14 shows how shrinking works in striped metalun components. Figure 14 LUN shrinking in striped metaluns After the shrink operation, each component will be shrunk by an equal size and the components will not be eliminated from the metalun. In a striped metalun, even though the space is reduced, the existing striping is maintained between the components. For example, a metalun is created by striping three 10 GB LUNs from different RAID groups, as shown in Figure 15. Applied Technology 9

10 Figure 15 metalun configuration This results in a metalun of 30 GB, as shown in Figure 16. Figure 16 metalun In this drive, 12 GB of space is shrunk as shown in Figure 17. Figure 17 Shrinking the metalun After shrinking through VDS, the drive size is updated at the OS level. Figure 18 Drive size The metalun capacity is also updated at the CLARiiON level. Figure 19 Capacity changes in the component LUNs Out of the three 10 GB component LUNs, each LUN is shrunk by 4 GB. This way, the space is equally shrunk in each of the component LUNs. Applied Technology 10

11 Concatenated metaluns In a concatenated metalun, each added component LUN is appended as a new addressable capacity of the metalun s base component. Concatenated metaluns can use component LUNs that are of a different RAID types and RAID sizes. In this case, CLARiiON writes only to one LUN at a time. LUN shrinking can be done on metaluns to free up the storage space. Figure 20 shows how the shrink operation works in a concatenated metalun s components. Figure 20 LUN shrinking in a concatenated metalun The LUN shrinking feature will shrink space from the components that are added from the last to the first. Components that are less than the shrinking capacity are unbound and removed from the metalun. To claim the space from the unbound LUNs, the RAID groups where the unbound LUNs were created must be defragmented. For example, a 40 GB LUN is created by concatenating three LUNs: one 5 GB, one 15 GB, and one 20 GB LUN from different RAID groups. Concatenation involves combining LUNs from different RAID groups instead of a single RAID group. Figure 21 MetaLUN configuration This metalun is shown as 40 GB when it is presented to the host as a drive. Applied Technology 11

12 Figure 22 MetaLUN presented as a drive When performing a volume shrink, the amount of space to shrink is specified as 17 GB instead of the default available shrink size of 20 GB. Figure 23 Shrinking the metalun After the volume shrink, a partition of 17 GB is created on the drive. Figure 24 After host side shrinking After the LUN shrinking is done using the diskraid command, the capacity changes are made at the CLARiiON level. On the metalun, of the three LUNs (5 GB, 15 GB, and 20 GB), the 5 GB LUN is removed and the 20 GB LUN is shrunk to 8 GB. The shrunk size of the 20 GB LUN is highlighted in Figure 25. Figure 25 Component LUN size after shrinking Based upon our study of the previous scenarios, the shrinking process of the CLARiiON LUN depends on whether the LUNs are combined using striping or concatenation. In the case of striped metaluns, after shrinking, the remaining space is equally distributed to the component LUNs. But in the case of the concatenated metalun, the shrinking feature removes the least sized component LUN and shrinks the remaining space from the component LUN that was added last into the meta. Applied Technology 12

13 Additional considerations for LUN shrinking The following points on supportability, performance, and resiliency must be considered for all LUN shrinking use cases: LUN shrinking is currently supported only in Microsoft Windows Server Note: This is true at the time this document is written. The capacity changes due to LUN shrinking occur as a background process. A shrink operation will not be automatically restarted in the event of a system failure. Currently the LUN shrinking feature is not directly available through Navisphere Manager. Because the command works through the CLI, there is no visible progress update of the operation. CLARiiON private LUNs, snaps, clones, and mirrors cannot be shrunk. CLARiiON spin down must not be enabled for the LUN that is to be shrunk. A single shrink request can be done at a time for each RAID group. There may be many shrink requests running in parallel for different RAID groups. There should be no trespassing, that is, changing the ownership of the LUNs during the LUN shrinking process. There must be a difference of at least 16 MB from the current internal capacity for a shrink request to be successful. LUN shrinking with Microsoft Exchange is usually considered as an ever-expanding and never-shrinking pool of loosely structured information. As users, we have become accustomed to large attachments, and being able to instantly go back to a conversation to reference some important information. This context seems to be an odd place to talk about shrinking LUNs. On the other hand, expanding the LUNs seems like a much better idea here. With the introduction of EMC SourceOne archiving for Exchange, it becomes clear why LUN shrinking can be useful here. High-speed production storage is expensive for IT departments, and most Exchange deployments use plenty of it. EMC SourceOne allows older data and large chunks of data-like attachments to be replaced with shortcuts in Exchange that refer to the same object on a less expensive tier of storage. In this case, we may wonder what to do with the heavily under-utilized and very expensive LUNs, which until recently held all this data. This is where LUN shrinking comes into the picture. Obviously, we must not shrink the LUNs to their minimum size because mail storage tends to grow. But, if you need to reallocate some storage, LUN shrinking can be very useful. Note: Shrinking an Exchange database by the default free size will result in a minimally sized LUN, which will immediately cause the Exchange server to unmount the database. The following tests simulate a typical Exchange environment with 2,000 mailboxes and a very heavy user profile workload. To understand how LUN shrinking is performed, a basic understanding of the database disk configuration is required. There are four component LUNs in the database metalun. Each database metalun is 335 GB, and the component LUNs are 83 GB. Using Microsoft LoadGen, a user activity was simulated for 10 hours. In the middle of the LoadGen test, the database LUN size was reduced by 100 GB. After the CLARiiON LUN shrinking operation was completed, the database disk shrunk to 235 GB as expected. At the CLARiiON level, out of the four component LUNs of 83 GB, the last LUN was removed. After shrinking, the remaining component LUNs were as follows: two 83 GB LUNs and one 67 GB LUN. Applied Technology 13

14 Figure 26 LoadGen test During the test run, LUN shrinking was performed. There were no execution errors reported during or after the test run. Databases were not dismounted. The result shows that there was no downtime for Exchange databases and Outlook users due to LUN shrinking. The variation of database disk I/O operations per second (IOPS) is illustrated in Figure 27: Figure 27 Exchange database IOPS The number of completed IOPS declined by approximately 30 percent during the test. So, it is recommended to complete shrinking operations during the non-peak hours. Figure 28 shows the variation of read and write latencies on the database LUN. Applied Technology 14

15 Figure 28 Exchange database read/write latencies The average database write latency showed a minimal impact due to the shrink operation. However, the database read latency, which is often a reliable proxy for customer experience, shows a 67 percent increase during the operation. This supports the recommendation from the previous result that while a shrink operation can be executed sucessfully while under load, it must be scheduled for non-peak hours, if possible. Conclusion LUN shrinking will significantly improve the storage utilization of a system by enabling storage administrators to reclaim any unused storage space inside a CLARiiON LUN. LUN shrinking is a two-step process that needs to be started from the host side and completed on the array side. This paper describes the steps to shrink a CLARiiON LUN. Overprovisioning storage to business-critical applications is a common practice in the implementation of high-performance storage solutions. Tests conducted with business-critical applications like Microsoft Exchange prove that using the LUN shrinking feature will have minimum performance impact on the applications with zero data loss. This allows the allocation of storage space to closely match the actual needs of the application. By reducing the amount of unused capacity available to high-performing applications, businesses can realize improved storage efficiency and reduce their total cost of ownership for the solution. References EMC VDS Provider Release Notes EMC CLARiiON Best Practices for Performance and Availability: Release 29.0 Firmware Update Applied Best Practices white paper EMC CLARiiON Storage System Fundamentals for Performance and Availability Applied Best Practices white paper EMC CLARiiON MetaLUNs A Detailed Review white paper Applied Technology 15