HP XP P9500 Storage - Manual (Page 42)

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For mainframe volumes, each Cache Residency cache extent must be defined on contiguous
tracks, with a minimum size of one cache slot (or track) and a maximum size of one LVI. This
is equivalent to 66 KB.
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For OPEN-V volumes, Cache Residency cache extents must be defined in logical blocks using
logical block addresses (LBAs), with a minimum size of 512 LBAs (equivalent to 264 KB).
However, in most cases you will assign an entire open-system volume for Cache Residency.
If the remaining cache memory is less than 256 MB, Cache Residency is not available.
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You can prestage the data to the resident cache area. If prestaging is not used, the data will
be loaded into the Cache Residency extents when the first "miss" occurs. If prestaging is used,
performance may be affected for a short time while the data is read into Cache Residency
cache.
CAUTION: Prestaging of Cache Residency data should not be performed during peak
activity.
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All write I/Os to Cache Residency data are duplex writes, guaranteeing full data integrity.
The Cache Residency data remains fixed in cache until you manually delete it. Deletion of
Cache Residency extents will destage any write data to the affected volume(s).
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It is possible to expand the amount of Cache Residency cache without canceling the existing
Cache Residency settings. Contact HP Technical Support for more information.
Cache Residency system specifications
The table below outlines the system specifications for cache residency.
Specification Item
Mainframe system Open system
3380-3, 3A, 3B, 3C OPEN-V Emulation Type
3390-3, 3A, 3B, 3C, 3R, 9, 9A, 9B, 9C, L,
LA, LB, LC, M, MA, MB, MC, A OPEN-3, 8, 9, E, L
Virtual LVI volume LUN Expansion (LUSE) volume Supported volumes
Virtual LUN volume
At least one cache slot (or track): Equivalent
to 66 KB.Up to 1 LDEV. For OPEN-V, at least 512 LBAs:
Equivalent to 264 KB Unit of cache area allocation
For other than OPEN-V, at least 96 LBAs:
Equivalent to 66 KB
Per storage system: 16,384 Number of cache areas
Per LDEV: 4,096
42 Estimating cache size