chvol - Changes the attributes of a volume
/sbin/chvol [-l] [-r blocks] [-w blocks] [-t blocks] [-c
on | off] [-A] special domain
Activates a volume after an incomplete addvol or rmvol
operation. Turns I/O consolidation mode on or off. Displays
the range of I/O transfer sizes, in 512-byte blocks,
as calculated by the kernel, based on the disk's geometry:
rblks displays the minimum, the maximum, and the
preferred transfer size for reads.
wblks displays the minimum, the maximum, and the
preferred transfer size for writes. Specifies the
maximum number of 512-byte blocks that the file
system reads from the disk at one time. If smoothsync
is enabled on the domain (smoothsync_age is
non-zero), this switch should not be used as the
smoothsync algorithms make its use obsolete. If
smoothsync is not enabled on the domain, this
switch specifies how many 512-byte blocks of dirty
data will be cached in memory for this volume
before they are written to permanent storage. The
current value of this variable is the output value
thresh (threshold). The number of blocks specified
must be in multiples of 16. The valid range is
0-32768. The default (when a volume is added to a
domain) is 16384. Specifies the maximum number of
512-byte blocks that the file system writes to the
disk at one time.
Specifies the block special device name, such as
/dev/disk/dsk2c. This command supports shorthand device
names for block special devices. For example, if you enter
dsk2g, it will be translated to /dev/disk/dsk2g. Specifies
the name of the domain.
The chvol command can be run at anytime to change the
attributes of a volume in an active domain; the system
does not have to be quiescent. If you attempt to change
the attributes of a volume in a domain that is not active,
an error message is produced.
The initial I/O transfer parameter for both reads and
writes is typically 128 or 256 blocks, depending on the
disk driver's preferred I/O transfer rate. Once you
change the I/O transfer parameters with the -r option or
the -w option, the parameters remain fixed until you
change them again. The values for the I/O transfer parameters
are limited by the device driver. Every device has a
minimum and maximum value for the size of the reads and
writes it can handle. If you set a value that is outside
of the range that the device driver allows, the device
automatically resets the value to the largest or smallest
it can handle.
By default, the I/O consolidation mode (cmode) is on. The
cmode must be on for the I/O transfer parameters to take
effect. You can use the -c option to turn the cmode off,
which sets the I/O transfer parameter to one page.
Interrupting an rmvol operation can leave the volume in an
inaccessible state. If a volume does not allow new allocations
after an rmvol operation, use the chvol command with
the -A option to reactivate the volume.
Using the chvol command without any options displays the
current cmode and the I/O transfer parameters.
This command supports shorthand names for LSM volume
names. For example, if you enter the following: # chvol
the volume name will be translated to: # chvol
The values for the wblks and rblks attributes are limited
by the device driver.
You must be the root user to use this command.
The following example displays the cmode and the I/O
transfer parameters of the /dev/disk/dsk1c volume in the
domain1 domain: # chvol /dev/disk/dsk1c domain1 rblks =
128 wblks = 128 cmode = on thresh = 16,384 The following
example additionally toggles the cmode: # chvol -c off
/dev/disk/dsk1c domain1 # chvol /dev/disk/dsk1c domain1
rblks = 128 wblks = 128 cmode = off thresh = 16,384 The
following example continues by changing the I/O transfer
parameters of reads (rblks) and writes (wblks) from 128
blocks to 256 blocks. Note that the cmode is off and must
be on before the parameters take effect: # chvol -r 256 -w
256 -c on /dev/disk/dsk1c domain1 chvol /dev/disk/dsk1c
domain1 rblks = 256 wblks = 256 cmode = on thresh =
16,384 The following example shows the I/O transfer range
on domain1: # chvol -l /dev/disk/dsk0a domain1 chvol
/dev/disk/dsk0a domain1 rblks: min = 16 max = 32768 pref
= 256 wblks: min = 16 max = 32768 pref = 256
[ Back ]