HP 200 Storage Virtualization System - Manual (Page 11)

1 Overview of XP Disk/Cache
Partition
HP StorageWorks XP Disk/Cache Partition enables logical partitioning of the resources in the array. HP
StorageWorks XP Disk/Cache Partition contains the cache logical partition function (CLPR) and the
storage management logical partition function (SLPR).
The cache logical partition function enables you to partition the built-in cache memory in the array
into multiple virtual cache memories. By allocating the partitioned virtual cache to a host, the I/O
performance of other hosts can be protected from decreasing even if one host issues many I/O requests.
The storage management logical partition function enables you to partition an array into multiple virtual
arrays. By having multiple virtual arrays, your data is better protected from risks, such as accidently
destroyed data.
XP Disk/Cache Partition features
XP Disk/Cache Partition has two components:
• Cache logical partitions (CLPRs)
• Storage management logical partitions (SLPRs)
Cache logical partitions (CLPRs)
If one array is shared with multiple hosts, and one host reads or writes a large amount of data, the
host's read and write data might occupy a large area in the array's cache memory. In this situation,
other hosts slow down the read/write speed because other hosts must wait to write to cache memory.
To prevent this situation, the cache logical partition function in XP Disk/Cache Partition partitions the
array's cache memory. Partitioned cache memories are used as virtual cache memories, and each of
them is allocated to each host. As a result, this prevents the situation where the specified host exclusively
uses most of cache memory.
Figure 1 shows how a corporation's cache memory is partitioned to three virtual cache memories.
Each virtual cache memory is allocated to each host in the three branch offices. Branch A's host is
inputting and outputting a large amount of data to or from the array. However, the read and write data
of Branch A's host does not occupy cache memory because the cache capacity that Branch A's host
can use is limited to 40 GB. Even if Branch A's host accesses a large amount of data, the hosts of other
branches do not slow down the read/write speed because of the amount of data Branch A is accessing.
The hosts of other branches can always use up to 40 GB of cache area.
IMPORTANT:
Disk/cache partitioning for the SVS200 can be increased up to 8 CLPR and SLPRs with additional
licensing (the SVS200 ships with a license for one SLPR and four CLPRs).
The virtual cache memory that the cache logical partition function partitions is referred to as the CLPR.
Up to 32 CLPRs including CLPR0 which is provided as a default can be created in one subsystem. For
more information, see Creating CLPRs .
HP StorageWorks 11