Optimizing Symmetrix system performance
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Performance and Optimization
Migration and relocation are based on Optimizer swap technology
and share the same requirements as the traditional swap
environment. Dynamic Relocation Devices (DRV’s) must be available
to provide additional protection during the data movement process.
Only devices with a matching sized DRV are eligible for Optimizer,
Virtual LUN control. RAID 6 devices are an exception and do not
require a DRV, since the two parity devices already provide double
protection.
Virtual LUN operations consume array resources and user definable
limits can be placed on such resource expenditure. The maximum
number of volumes that can be moved each day and the maximum
simultaneous volumes to be moved, work together to determine
resources that are used for the process. A priority value can also be
assigned to the copy process of each participant volume. Together,
these parameters affect how long a migration or relocation will take.
The Symmetrix configuration lock will remain in place while the
Virtual LUN data movement is in progress. If other configuration
management functions are routinely scheduled, the Virtual LUN
process should be limited by the maximum simultaneous volumes
and maximum number of volumes to ensure completion within a
timeframe that would allow the configuration lock to be released for
other activities. Virtual LUN functionality moves the logical volume
as a complete entity, including all mirrors of the device. Subsets of
data that reside on the logical volumes remain unknown to the
process. Consequently, users are advised to understand data
placement and assign related data to grouped logical volumes. At
present, the following manual exclusions apply when constructing
Virtual LUN migration lists:
â—† The protection types must be the same for the high performance
disks being migrated from and the high capacity disks being
migrated to.
â—† While microcode 5772 supports the migration of metadevices, an
individual meta member may not be specified as a volume to be
migrated.
â—† Physical disks containing the volumes to be migrated may not be
specified as a destination physical disk.
â—† When specifying unmapped/unmasked to be TRUE, there must
be sufficient devices of the same RAID protection type to
complete the migration.
â—† The number of volumes that can be migrated at one time is
limited by the Optimizer parameter Max Simultaneous Swaps.
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