Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

Table 15-1
Kernel tunable parameters for VxVM (continued)
DescriptionParameter
The maximum number of volumes that can be created
on the system. The minimum and maximum permitted
values are 1 and the maximum number of minor
numbers representable on the system.
The default value is 8388608.
vol_max_vol
The maximum size of logical I/O operations that can
be performed without breaking up the request. I/O
requests to VxVM that are larger than this value are
broken up and performed synchronously. Physical I/O
requests are broken up based on the capabilities of the
disk device and are unaffected by changes to this
maximum logical request limit.
The default value is 2048 sectors (2048KB).
The value of voliomem_maxpool_sz must be at least
10 times greater than the value of vol_maxio.
If DRL sequential logging is configured, the value of
voldrl_min_regionsz must be set to at least half
the value of vol_maxio.
vol_maxio
The maximum size of data that can be passed into
VxVM via an ioctl call. Increasing this limit allows
larger operations to be performed. Decreasing the limit
is not generally recommended, because some utilities
depend upon performing operations of a certain size
and can fail unexpectedly if they issue oversized ioctl
requests.
The default value is 32768 bytes (32KB).
vol_maxioctl
The number of I/O operations that the vxconfigd
daemon is permitted to request from the kernel in a
single VOL_VOLDIO_READ per VOL_VOLDIO_WRITE
ioctl call.
The default value is 256. This value should not be
changed.
vol_maxparallelio
Performance monitoring and tuning
Tuning VxVM
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