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EMC Proven Professional Knowledge Sharing 2010 LUN Shrinkage with EMC CLARiiON CX400 Series Markus Langenberg Markus Langenberg Senior Product Manager Fujitsu Technology Solutions
EMC Proven Professional Knowledge Sharing 2010
LUN Shrinkage with EMC CLARiiON CX400 Series
Markus Langenberg
Markus LangenbergSenior Product ManagerFujitsu Technology Solutions
2010 EMC Proven Professional Knowledge Sharing 2
Table of contents
Requirements ................................................................................................................................ 3
Pre configuration tasks ................................................................................................................ 3
DiskRAID utility ............................................................................................................................. 6
Shrinking the LUN......................................................................................................................... 9
Eliminating MetaLUN components by shrinking MetaLUNs ................................................ 13
Shrinkage example ..................................................................................................................... 17
Hints .............................................................................................................................................. 18
Restrictions .................................................................................................................................. 18
Limits ............................................................................................................................................ 19
NaviSECCLI Command ............................................................................................................. 20
Disclaimer: The views, processes or methodologies published in this compilation are those of the authors. They do not necessarily reflect EMC Corporation’s views, processes, or methodologies
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Introduction
You can shrink LUNs that are mapped to a host with the new FLARE R29 revision. The first
step is to shrink the host accessible volume space. Afterwards, the underlying storage will be
freed by reducing the capacity of a FLARE™ LUN. This is managed by using operating
system and storage APIs such as the VDS (Virtual Disk Service) provider. This is necessary
to detect the size of capacity reduction, to ensure no host I/O is present before and during
shrink operations, and to ensure that no host data is deleted.
Requirements • Microsoft Windows 2008 and included DiskRAID utility • CLARiiON® CX4 Series storage array with FLARE Release R29 or higher • EMC Solutions Enabler with VDS Provider Version 4.1.1
Pre-configuration tasks Install Solution Enabler with VDS Provider
Select the appropriate Solution Enabler package and run the executable. The EMC Solutions Enabler with VDS Provider welcome page appears, prompting you to install Solutions Enabler with VDS Provider version 4.1.1. Click Next.
The Destination Folder page appears prompting you to select an install directory. I recommend accepting the default directory. Select the install directory and click next.
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The Setup type page appears. Select the appropriate radio button for the installation (Typical, Custom or complete).
For custom setup, select the program features that will be installed. Click next.
The Service list page appears. Select the appropriate checkbox for the desired service. Click Next to continue or Cancel to exit the installation. The EMC Solutions Enabler Event Daemon service is required for proper functioning. Therefore, leave the EMC Solutions Enabler Event Daemon checkbox enabled.
The Ready to install the program page appears. Click install to begin the installation. Afterwards, press Finish to exit setup. The installation of the Solution Enabler with integrated VDS Provider is done.
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Solution Enabler Post-installation Tasks Solutions Enabler needs to authorize the managed CLARiiON CX4 arrays. Use the SYMCLI
symcfg command to authorize Solutions Enabler access to the CLARiiON CX storage array.
See the following example.
You must add authorization for each of the CLARiiON CX4 storage processors. Creating RAID and Storage Groups One RAID Group with LUNs demonstrates the LUN shrinkage feature. These LUNs were
added to the Storage Group, together with the Windows 2008 host.
All LUNs were formatted and a drive letter assigned via Windows Disk Manager. Disks 2 to 5 are the LUNs from the CLARiiON CX4-120.
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DiskRAID utility DiskRAID is a CLI tool that allows you to configure and manage RAID storage subsystems.
It uses the storage vendors’ VDS providers to manage storage subsystems.
You can check whether the VDS providers are successfully installed and can be used by
DiskRAID with the following command.
Here is a list of subsystems that are registered with EMC Solutions Enabler (Both SPs):
To get more information about one SP (e.g. Subsys 1), select it from the CLI.
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Now you can list the LUNs that are managed by the subsystem.
You can see the device numbers that equal that disk numbers in the Windows disk manager
in the last column.
You must select the desired LUN to get a detailed view.
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Afterwards, you can view the detailed information when running the following command.
Important: Some values reported by DiskRAID do not equal the values you see in the
Navisphere® Manager. For example, partition S:\ (Disk 5) is LUN 23 on the storage system
(page 4). But the DiskRAID utility reports that partition (device/disk 5) as LUN 19. You must
to select to correct LUN when doing the shrinkage. Compare the LUN identifier in the upper
screenshot with the LUN UniqueID in the Navisphere Manager (LUN properties) to be safe.
Alternately, check the LUN name of the “detail lun” output; it matches the LUN name in
Navisphere Manager.
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Shrinking the LUN The first step is to reduce the volume size to the desired value. This is done via the Windows
disk manager. It is possible to shrink basic or dynamic volumes. Dynamic volumes can be
single dynamic or spanned dynamic.
To reduce the volumes capacity, right click on the volume and select “Shrink Volume…” from
the context menu.
In the next step, enter the amount of space to shrink. The shrink volume size must be equal
or less than the “Size of available shrink pace in MB” value. This is half the volume size at
maximum.
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The volume has the new size after the shrinkage; the freed space is unallocated.
After shrinking the volume size, you must shrink the corresponding LUN on the storage
array. At this point, the LUN on the storage is still the old size.
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The following command shrinks the LUN by the amount of megabytes specified in the
command. Use one of the recognized suffixes (B, KB, MB, GB, TB, PB) to specify the size.
Be sure to select the correct LUN; it is indicated by the asterisk before the first column.
The new LUN size is displayed in Navisphere Managers’ LUN properties.
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After rescanning the disks in the Windows Disk Manager, the previous unallocated space is
gone and the whole volume has the desired size.
Gaps are one disadvantage of shrinking LUNs, especially when they are located in the
middle of a RAID Group. I recommend defragging the RAID Group to achieve the maximum
LUN size available.
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Eliminating MetaLUN Components by Shrinking MetaLUNs Shrinking a MetaLUN results in deleting its components. The following examples show how
MetaLUN components are deleted after shrinkage.
The MetaLUN 2 consists of 4 components (LUN5, 6, 7 & 8). The LUN size is:
• LUN 5 : 20 GB • LUN 6 : 20 GB • LUN 7 : 10 GB • LUN 8 : 5 GB
The Windows Disk Manager recognizes a 55 GB disk (Disk 5) in total.
To eliminate the last component of the MetaLUN (LUN 8) the disk is shrunk by 5 GB.
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Result after the shrinkage from the disk manager perspective.
The LUN size of the storage array is still 55 GB; use the DiskRAID utility to shrink it.
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The MetaLUN size is reduced to 50 GB after shrinkage (screenshot below). As a result, the
last component (LUN 8) was removed from the MetaLUN.
The total disk size reported by the windows disk manager is also 50 GB.
This procedure can be repeated by shrinking the disk again by 10 GB. As result, the last
component of the MetaLUN will be reduced by 10GB. It will be deleted and removed from the
MetaLUN as this is exactly the size of the component.
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A reduction of a MetaLUN is always based on a components level. This means if a
component consists of several LUNs (Concatenated), a reduction of this component will
reduce each LUN equally.
Example:
This MetaLUNs component consists of several LUNs (striped). Each LUN is 5 GB in size. When shrinking the MetaLUN by 5 GB the last LUN (LUN 9) will not be deleted. Every LUN is reduced in equal parts.
So, 5120 MB divided by 6 makes the reduction per LUN. As result every LUN has a size of round about 4150 MB after the shrinkage.
Please see the following page for an illustration of shrinkage.
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Shrinkage example
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Hints When you shrink a MetaLUN more than the last component size, it will reduce the capacity of
the next LUN as well.
For example, when a MetaLUN that consist of three components (component 0: 20 GB,
component 1: 20 GB, component 2: 10 GB) is shrunken by 15 GB, the component 2 will be
completely eliminated and component 1 will be reduced by 5 GB).
The maximun shrink size of a disk is either the half capacity or the free capacity. It is not
possible to shrink a disk that contains more data than the free capacity.
Supported Configurations:
• LUN shrink is supported on all RAID Types and all CLARiiON CX4 models
• FLARE supports multiple shrink requests on the same LUN
• FLARE supports parallel shrink requests on LUNs in the same RAID Group
• LUN shrinking is supported while Background services are running (except RAID
Group expansions/Defrags)
o Background Services: LUN zeroing, Background verifies, sniff verifies,
Hot spare, rebuilds, equalizes, Proactive Copy
• Shrink request supports shrink in TB, GB, MB, block size
o Minimum to shrink is to 1 block
• Shrink requests are returned successfully to the host if RG expansions/defrags
are in progress at that time
• MetaLUNs with any number of LUNs and component stripe width supported
o Configured User Capacity reflects the Shrunk Size of the DISKRAID.exe
shrink command
o Total User Capacity and Total Physical Capacity are updated
Please see the following page for Restrictions.
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Restrictions
• No I/Os in region to shrink
• For FLARE LUNs, shrink to size (desired LUN size) must be greater than 1 block
• For MetaLUNs, shrink to size must be less that Actual User Capacity
o If a Configured User Capacity exists, this is the Upper Limit, not the Total User
Capacity
o Not in Shutdown or Expanding State
• If a RAID Group expansion/defrag is initiated during an active shrink operation,
the request will be pended
o Note: A RAID Group defrag is not performed automatically after a LUN shrink
completes
• A shrink request is rejected if the FLARE or MetaLUN is expanding or migrating
• No Layered Applications (SnapView™, SAN Copy™, MirrorView™) can be active
on the LUN
o No thin LUN support for Release 29
Limits with FLARE R29
Model CX4-120 CX4-240 CX4-480 CX4-960
Configuration
Max LUNs per Comp 32 32 32 32
Max Comp per Volume 8 8 16 16
Max LUNs per Volume 256 256 512 512
Shrink Effort
Max LUNs to shrink 32 32 32 32
Max LUNs to unbind 224 224 480 480
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NaviSECCLI Command Command: chglun –l <lun> [-sq tb|gb|mb|bc] -shrinkto <capacity>
Parameters: -sq tb|gb|mb|bc (tb: terabytes, gb: gigabytes, mb: megabytes, bc: block count)
-shrinkto (New shrink capacity; Match size qualifier above)
Example: naviseccli -h 172.26.96.170 -user Administrator -password XXXXXX -scope 0
chglun -l 1 –sq gb -shrinkto 10
This command is used by Windows 2008 to shrink a volume on the CLARiiON CX4 storage
array. It also works when running the command directly from the NaviSECCLI prompt.
However, I do not recommend it as the operating system is not involved in this process. Use
the DiskRAID utility in conjunction with the VDS Hardware Provider to reduce the LUN
capacity.
