Filter
Top Products
149Administering dynamic multipathing (DMP)
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:
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
Partition size in blocks Equivalent size in bytes
22,048
44,096
88,192
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