HP XP Array Manager Software - Manual (Page 18)

To identify the exact number of LBAs in an LDEV, you must first display the Reports Display window
and search for the parity group to which the LDEV belongs according to the LDKC, control unit
(CU), and LDEV numbers.
Next, you must display the Customized Volume window and find the exact number of LBAs in the
LDEV. For further information about the Reports Display window, see the HP StorageWorks
XP24000/XP20000 Remote Web Console User Guide. For further information about VLL, see the
HP StorageWorks XP24000/XP20000 Virtual LVI/LUN (VLL) and Volume Shredder User Guide.
As illustrated in “Example of LBA Value Setting When Using LUSE” (page 17) , the LUSE volume is
composed of three LDEVs: 00:01 (1,000 LBAs), 00:02 (1,002 LBAs), and 00:03 (1,020 LBAs).
If you see from the host and want to set Cache Residency to 500 LBAs starting from No. 1,020
LBA, you can set the Cache Residency to 500 LBAs starting from No. 20 LBA of the second LDEV
because the first LDEV size is 1,000 LBAs.
The following Virtual LVI/LUN (VLL) operations automatically reset Cache Residency cache:
•
When a fixed or customized volume that is partly or wholly assigned to Cache Residency is
converted into free space by the VLL Volume to Space function.
•
When a VDEV containing volumes that are assigned to Cache Residency is initialized by the
VLL Volume Initialization function.
For further information on Virtual LVI/LUN, see the HP StorageWorks XP24000/XP20000 Virtual
LVI/LUN (VLL) and Volume Shredder User Guide.
Caution: You may want to increase total storage system cache capacity when using Cache Residency
to avoid data access performance degradation for non-Cache Residency data. Cache Residency
is only available on storage systems configured with at least 512 MB of cache. Your HP service
representative configures the maximum allowable Cache Residency area when the cache is installed.
Note: OPEN-V logical blocks are in 128-byte increments. Cache Residency Manager recognizes
open-system logical blocks in 512-block increments. For example, if you enter a starting LBA as 1
and an ending LBA as less than 512, Cache Residency automatically changes the beginning LBA
to 00 and the ending LBA to 511.
HP StorageWorks XP Disk/Cache Partition Support Requirements
The volume used for the Cache Residency Manager function varies based on user type.
If you are logged in to Remote Web Console as a storage administrator, you can apply the Cache
Residency Manager function to all volumes. If you are logged in to Remote Web Console as a
storage partition administrator, you can apply this function to the volumes in the CLPR that you
administer. In this case, you cannot perform the pre-staging function.
Note: You can use the Cache Residency Manager function only if the volume and the cache are
allocated into the same CLPR.
18 Preparing for Cache Residency Manager Operations