HP Veritas Volume Manager 5.0 -UX 11i v3 enc0, balanced, partitionsize=2048, Partition size in blocks, Equivalent size in bytes, dmp_pathswitch_blks_shift

Administering dynamic multipathing (DMP) 149

Administering DMP using vxdmpadm

You can use the size argument to the partitionsize attribute to specify the partition size. The partition size in blocks is adjustable in powers of 2 from

2 up to 2^31 as illustrated in the table below:

Partition size in blocks	Equivalent size in bytes
2	2,048
4	4,096
8	8,192
16	16,384
32	32,768
64	65,536
128	131,072
256	262,144
512	524,288
1024 (default)	1,048,576
2048	2,097,152
4096	4,194,304

The default value for the partition size is 1024 blocks (1MB). A value that is not a power of 2 is silently rounded down to the nearest acceptable value. Specifying a partition size of 0 is equivalent to the default partition size of 1024 blocks (1MB). For example, the suggested partition size for an Hitachi HDS 9960 A/A array is from 16,384 to 65,536 blocks (16MB to 64MB) for an I/O activity pattern that consists mostly of sequential reads or writes.

Note: The benefit of this policy is lost if the value is set larger than the cache size.

The default value can be changed by adjusting the value of a tunable parameter (see “dmp_pathswitch_blks_shift” on page 476).

The next example sets the balanced I/O policy with a partition size of 2048 blocks (2MB) on the enclosure enc0:

# vxdmpadm setattr enclosure enc0 iopolicy=balanced \

partitionsize=2048