IBM DS8700, Introduction And Planning Manual

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Functions and features of Easy Tier: manual mode
This section descries the functions and features of Easy Tier in manual mode.
Volume migration
Volume migration for restriping can be achieved by:
v
Restriping - Relocating a subset of extents within the volume for volume
migrations within the same pool.
v Rebalancing - Redistributing the volume across available ranks. This feature
focuses on providing pure striping, without requiring preallocation of all the
extents. This means that you can use rebalancing when only a few extents are
available.
You can select which logical volumes to migrate, based on performance
considerations or storage management concerns. For example, you can:
v Migrate volumes from one extent pool to another. You might want to migrate
volumes to a different extent pool that has more suitable performance
characteristics, such as different disk drives or RAID ranks. For example, a
volume that was configured to stripe data across a single RAID can be changed
to stripe data across multiple arrays for better performance. Also, as different
RAID configurations become available, you might want to move a logical
volume to a different extent pool with different characteristics, which changes
the characteristics of your storage. You might also want to redistribute the
available disk capacity between extent pools.
Notes:
– When you initiate a volume migration, ensure that all ranks are in the
configuration state of Normal in the target extent pool.
– Volume migration is supported for standard and ESE volumes. There
is no direct support to migrate auxiliary volumes. However, you can
migrate extents of auxiliary volumes as part of ESE migration or rank
depopulation.
– Ensure that you understand your data usage characteristics before you
initiate a volume migration.
– The overhead that is associated with volume migration is comparable
to a FlashCopy operation running as a background copy.
v
Change the extent allocation method that is assigned to a volume. You can
relocate a volume within the same extent pool but with a different extent
allocation method. For example, you might want to change the extent allocation
method to help spread I/O activity more evenly across ranks. If you configured
logical volumes in an extent pool with fewer ranks than now exist in the extent
pool, you can use Easy Tier to manually redistribute the volumes across new
ranks that have been added.
Note: If you specify a different extent allocation method for a volume, the new
extent allocation method takes effect immediately.
Manual volume rebalance using volume migration
Volume and pool rebalancing are designed to redistribute the extents of volumes
within a non managed pool. This means skew is less likely to occur on the ranks.
Notes:
Chapter 3. Data management features
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