Considerations in planning to create Thin Pools:
• The underlying structure of Thin Pools are made up of whats called ‘Data Devices’ (TDAT’s). These devices provide the actual physical storage used by Thin Devices (TDEV’s).
• A Thin Pool can only be configured with one disk type.
• Thin Pools may only consist of Data devices with the same emulation and protection type. Thus TDAT’s with a protection type of RAID-1, RAID-5, or RAID-6 will be used to create a Pool. TDEV’s inherit the protection type of the TDAT’s used in the pool. The differenet emulation types are fba, ckd, as400 and celerra. The Most commonly used emulation type is FBA, this is what your open systems use ( Unix/Linux, vSphere, Windows).
• Data devices that make up a pool may be of different sizes but it is recommended that all data devices in a pool are of the same size to ensure even data distribution.
• Data devices are not visible to hosts and cannot be used until they are assigned to a Pool.
• TDAT’s should be spread evenly across DAs and drives. The wide striping provided by Virtual Provisioning will spread thin devices evenly across the data devices. Ensuring that the TDATs are spread evenly across the back end will result in best performance.
• The balance of the pools is very important – Each pool should be spread over disks evenly. That is to say every disk in the pool should have the same number of TDATs on it. If one disk has twice as many TDATs as another in the same pool, that disk will serve twice as many IOPs. Also every pool should have 8 splits/hypers active per disk, or the minimum number to use the whole disk.
• I think each disk should be used for one pool only, and there should just be one thin pool per technology to keep things simple. Note: There may be circumstances where a thin pool with multiple applications consisting of mixed type workloads utilizing the same underlying spindles does not favor a particular application and may result in inconsistent performance levels for that application; in this type of instance the application may require a dedicated thin pool.
• 512 Pool’s is the maximum that can be created in a VMAX.
• There is no limit to the number of thin devices that can be bound to a thin pool or data devices that can be added to a thin pool.
• The limit to the number of thin and data devices that can be configured is 64,000.
Given the following Thin Pool requirements I will detail how to create the Thin Pools and assign the TDAT ranges:
Firstly list the Disk Groups:
symdisk list -dskgrp_summary
Ensure the TDAT’s are availbale and have not been used in another Pool by issuing the -nonpooled cmd. The output will also display the RAID configuration of the datadevs:
symdev list -datadev -disk_group 2 -nonpooled
symdev list -datadev -disk_group 3 -nonpooled
symdev list -datadev -disk_group 4 -nonpooled
Create the Thin Pools
The Thin Pools can be created first without adding data devices, TDATs are added at a later time.The Pool name can contain a sequence of 1 to 12 alphanumeric or ‘-‘ (hyphen) or ‘_’ (underscore) characters.:
symconfigure -sid xxx -cmd “create pool Prod-HP-R53 type=thin;” COMMIT
symconfigure -sid xxx -cmd “create pool Prod-GP-R14 type=thin;” COMMIT
symconfigure -sid xxx -cmd “create pool Prod-AR-R66 type=thin;” COMMIT
Populate the Thin Pools with the defined TDAT’s
After creating the Pools, TDAT’s are added to the Pools and enabled:
symconfigure -sid xxx -cmd “add dev 00F0:017F to pool Prod-HP-R53 type=thin, member_state=enable;” COMMIT
symconfigure -sid xxx -cmd “add dev 0180:05FF to pool Prod-GP-R14 type=thin, member_state=enable;” COMMIT
symconfigure -sid xxx -cmd “add dev 0600:0943 to pool Prod-AR-R66 type=thin, member_state=enable;” COMMIT
Using the list command to display a list of the Thin Pools created utilizing the –thin option:
symcfg list -pools -thin -gb
View details of the newly created Pools
In this example, the newly created Pool’s are displayed along with details about the pool and the data devices that have been added to it. The –detail option displays any bound thin devices:
symcfg show -pool “Prod-HP-R53” -thin -detail -GB
symcfg show -pool “Prod-GP-R14” -thin -detail -GB
symcfg show -pool “Prod-AR-R66” -thin -detail -GB
View of Thin Pools from Unisphere: