Bind mode – HP XP Array Manager Software User Manual
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About Cache Manager Operations
2-5
Hitachi Cache Manager User’s Guide
Bind Mode
In Bind Mode, the total capacity of cache required is:
Standard cache + cache required for Cache Manager
In bind mode the cache extents are used to hold read and write data for
specific extent(s) on volume(s). Any data written to the bind area is not de-
staged to the disk. To ensure data integrity, write data must be duplexed in
the cache area, which consumes a significant amount of the cache.
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 priority mode; write operations do not have to wait for
available cache segments; and there will be no backend contention caused by
destaging data.
RAID-5/6. For RAID-5 and RAID-6 array groups the amount of cache
required is three times the space required for the user data. For RAID-5/6
mainframe volumes, one slot is 66 kB, which requires 12 cache segments
(16.5 kB/segment). For example, 16 slot images require 3,168 kB of reserved
cache.
•
Note: Even though tracks for 3390 LVIs are 56 kB, because cache is
divided into 16.5 kB segments, it will require four segments. Slots for 3380
LVIs are 46 kB, so three segments are sufficient.
•
Note: If a RAID-5/6 volume area is changed from priority mode to bind
mode and no cache is added, then only 33% of the user data will fit in the
area previously assigned for priority mode.
RAID-1 and external storage. For RAID-1/external array groups the
amount of cache required is two times the space required for user data. For
3390 volumes, One slot is 66 kB, which requires eight cache segments (16.5
kB/segment). For example, 16 slot images require 2,112 kB of reserved cache.
•
Note: If a RAID-1 volume area is changed from priority mode to bind
mode and no cache is added, then only 50% of the user data will fit in the
area previously assigned for priority mode, and the remaining 50% is used
to save read/write data.