chvol(8)chvol(8)NAMEchvol - Changes the attributes of a volume
/sbin/chvol [-l] [-r blocks] [-w blocks] [-t blocks] [-c on | off] [-A]
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 typi‐
cally 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 automat‐
ically 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 opera‐
tion, use the chvol command with the -A option to reactivate the vol‐
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 exam‐
ple, if you enter the following: # chvol testdg.vol1 dom1
the volume name will be translated to: # chvol /dev/vol/testdg/vol1
The values for the wblks and rblks attributes are limited by the device
You must be the root user to use this command.
The following example displays the cmode and the I/O transfer parame‐
ters 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 contin‐
ues 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