Cache Management - Fujitsu Siemens Computers pmn User Manual

Cache management

4.2 Cache management
This functionality enables individual cache file systems to be reserved for exclusive use by
particular LV groups.
LV groups which are not assigned to a cache file system are distributed to the remaining
caches ("FLOATING" setting).
LVG1
LV0001
LV0002
LV0003
...........
LV3000
Figure 28: Example of the exclusive use of the cache file system by LV groups
In concrete terms this means:
– An assignment of cache file system to LV group is defined by a configuration.
– An LV can be assigned to precisely one cache file system.
– Multiple LV groups can be assigned to a cache file system.
Possible applications:
"Location" of the logical volumes
●
The cache management function can be used to ensure that volumes are at a particular
location or on a particular RAID system.
Cache residence of the volumes
●
The volumes are always in the cache file system.
Benefit:
However, it must be ensured that the volume of data on the volumes does not exceed
the capacity of the cache file system.
70
Cache file system
FLOATING
/cache/101
Access to volumes of an LV group which is assigned to a particular cache
file system is extremely quick.
The reason for this is that the volumes are always in the cache file system.
The volumes are displaced only if the volume of data on these volumes
exceeds the capacity of the file system.
Selected system administrator activities
In this example the LV group
LVG1 is assigned the cache
file system /cache/101.
LVG4
LVG3
LV3001
The LV groups LVG2, LVG3
LVG2
LV3001
LV3002
and LVG4 are distributed to
LV3001
LV3002
LV3003
the remaining caches
LV3002
LV3003
...........
(FLOATING).
LV3003
...........
LV6000
...........
LV6000
LV6000
U41117-J-Z125-7-76