HP XP RAID Manager Software - Manual (Page 15)

Bind mode has the following advantages:
•
The accessibility of read data is the same as Cache Residency priority mode.
•
Write operations do not have to wait for available cache segments.
•
There is no back-end contention caused by destaging data.
In Bind Mode, the total capacity of cache required is:
standard cache + Cache Residency cache
For more information about calculating case size for bind mode, see “Estimating cache size”
(page 69) .
The next table specifies the cache requirements for bind mode operations:
Table 4 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 (for example,
3390-3, 3390-9)
= 198 KB = 12 cache
segments
Cache segments needed per
slot: 12 (slot capacity / cache
segment capacity)
Note: Even though a mainframe
track 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 bind data that has write attributes is normally not destaged. However, the data
is destaged in the following cases:
•
During cache blockage that is caused by certain maintenance operations (for example, cache
upgrades) or by cache failure.
•
If the storage system is powered off.
•
If the volume is deleted from Cache Residency bind mode.
Bind mode 15