HP XP P9500 Storage - Manual (Page 10)

is duplexed in the Cache Residency area, which consumes a significant amount of the Cache
Residency cache.
In Bind Mode, the total capacity of cache required is:
standard cache + Cache Residency cache
The following table specifies the cache requirements for bind mode operations. For further
information on calculating procedures for required cache size for using Cache Residency if the
bind mode is set, see
“Estimating cache size ” (page 38) . The primary advantage of bind mode
is that all targeted read and write data is transferred at host data transfer speed. In addition, the
accessibility of read data is the same as Cache Residency priority mode; write operations do not
have to wait for available cache segments; and there will be no back-end contention caused by
destaging data.
Table 2 Bind mode cache requirements
Cache Residency Cache
Requirement Capacity Specifications RAID Level or Volume
Type System Type
3 times the space required for
user data: 1 slot = 3 × 264 Slot capacity: 264 KB
Cache segment capacity: 16.5
KB
RAID 5 (3390) or RAID
6 OPEN Systems
KB = 792 KB = 48 cache
segments
Cache segments needed per
slot: 48 (slot capacity / cache
segment capacity)
2 times the space required for
user data: 1 slot = 2 × 264 Slot capacity: 264 KB
Cache segment capacity: 16.5
KB
RAID 1, or external
volumes
KB = 528 KB = 32 cache
segments
Cache segments needed per
slot: 32 (slot capacity / cache
segment capacity)
3 times the space required for
user data: 1 slot = 3 × 66 KB Slot capacity: 66 KB
Cache segment capacity: 16.5
KB
RAID 5 mainframe or
RAID 6 Mainframe (e.g., 3390-3,
3390-9)
= 198 KB = 12 cache
segments
Cache segments needed per
slot: 12 (slot capacity / cache
segment capacity)
Note: Even though a track for
mainframe is 56 KB, because
cache is divided into 16.5 KB
segments, it requires 4
segments.
2 times the space required for
user data: 1 slot = 2 × 66 KB Slot capacity: 66 KB
Cache segment capacity: 16.5
KB
RAID 1 mainframe, or
external volumes
= 132 KB = 8 cache
segments
Cache segments needed per
slot: 8 (slot capacity / cache
segment capacity)
Cache Residency that binds data and also has write attributes is not normally destaged. However,
this data will be destaged in the following cases:
•
During cache blockage that is caused by certain maintenance operations (e.g., cache upgrades)
or that is caused by cache failure.
•
If the storage system is powered off.
•
If the volume is deleted from Cache Residency bind mode.
10 About monitoring performance