HP XP7 Storage - Manual (Page 80)

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Host I/O response time
Performing Cache Residency operations on many LDEVs during host I/O may slow the host
I/O response time. To avoid degradation of response time, set only one LDEV at a time.
Deleting data from cache during host I/O may cause the response time of host I/O to become
slow. To avoid degradation of host response time, limit the amount of data you delete in one
operation as follows:
If the host timeout period is set to 10 seconds or shorter, limit the total amount of data to:
◦ 1 GB or less for open systems
◦ 1,000 cylinders or less for mainframe systems
If the host timeout period is set to 11 seconds or longer, limit the total amount of data to:
◦ 3 GB or less for open systems
◦ 3,000 cylinders or less for mainframe systems
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Minimum cache requirements
If the remaining cache memory after the cache residency operation will be less than 512 MB,
Cache Residency is not available.
Interoperability restrictions for cache residency
Behaviors Application
Do not perform the Business Copy or Business Copy Z Quick Restore operation on a
Cache Residency volume. Also, do not specify the Cache Residency setting on the Business Copy/ Business Copy
Z
volume on which the Business Copy or Business Copy Z Quick Restore operation is
performed. This operation swaps the internal locations of the source and target volumes,
which causes a loss of data integrity. For additional information, see the HP XP7
Business Copy User Guide or XP7 Business Copy for Mainframe Systems User Guide.
Do not perform the Auto LUN V2 operation on a Cache Residency volume. Also, do
not specify the Cache Residency setting on the volume on which the Auto LUN V2 Auto LUN
operation is performed. This operation swaps the internal locations of the source and
target volumes, which causes a loss of data integrity. For additional information, see
the HP XP7 Auto LUN User Guide and/or contact HP Technical Support.
The Cache Residency bind mode is not available to external volumes whose Cache
mode is set to Disable (which is the mode that disables the use of the cache when
there is an I/O request from the host). External Storage
Cautions and restrictions for prestaging
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Unsupported volumes
The prestaging function cannot be used for the following volumes:
◦ Thin Provisioning volume
◦ Thin Provisioning Z volume
◦ Smart Tiers volume
◦ Smart Tiers Z volume
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External volumes and storage system power off
When external volumes are configured in the storage system, you need to disconnect the
external storage system before powering off the storage system. If you power off the storage
system without performing the disconnect external storage system operation and then turn on
80 Cache Residency Manager operations