HP StorageWorks XP Remote Web Console Software - Manual (Page 60)

Deleting and remapping the external LU
You must delete and remap each LU that needs the cache setting changed. Using the information
recorded in
Collecting device information , delete and remap each LDEV.
1. On the LU Operation pane, select the appropriate external LU group number in the Device tree.
2. In the Device list, right-click the external LU that you want to delete, and select Delete LU ( Figure
21 ).
3. Click Apply.
4. Click either Yes or No. If you click Yes, skip the next step.
5. Click OK in response to the warning message.
6. Click OK.
7. Remap the LU using all the previous settings except for the cache mode setting, which is disabled.
See
Mapping external LUs (Add LU) .
NOTE:
When scanning for devices to add, the order in which devices are discovered might be
different. The UUID is always the same for the same external device. Ensure that the UUID
of the device being remapped matches the UUID that was deleted for the same LU number.
8. Recheck to ensure that the same external storage LUs (identified by UUIDs) are now assigned
their original settings and the desired cache mode. If not, delete and remap the external LU again.
Partitioning cache for external storage
Separate cache partitions isolate the applications that are using XP arrays and storage virtualization
systems from the I/O dampening effects of a cache that is filling up with host and internal I/O for
slower external targets. HP requires separate cache partitions (CLPRs) for:
• External volumes and internal XP volumes, except for configurations where all external storage
LUNs have cache disabled and do not have any external storage devices using data mirroring or
migration products
NOTE:
All HP 200 Storage Virtualization System volumes are external. Partition SVS200 cache according
to the other recommendations made in this section.
• External volumes that are used by XP data replication or data migration products, including XP
Business Copy, XP Continuous Access software products, XP Snapshot, XP Auto LUN, and XP
Tiered Storage Manager
• SVS200 source volumes and data copy or target volumes that have slower throughput
For example, Company A uses:
• XP10000 internal disks for database applications
• EVA3000 for backup applications
Cache can be partitioned for Company A as follows:
Managing cache with external storage 60