NAME

chvol − Changes the attributes of a volume

SYNOPSIS

/sbin/chvol [−l] [−r blocks] [−w blocks] [−t blocks] [−c on | off] [−A] special domain

OPTIONS

−AActivates a volume after an incomplete addvol or rmvol operation. 

−c on | off
Turns I/O consolidation mode on or off. 

−lDisplays 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. 

−r blocks
Specifies the maximum number of 512-byte blocks that the file system reads from the disk at one time.

−t blocks
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. 

−w blocks
Specifies the maximum number of 512-byte blocks that the file system writes to the disk at one time.

OPERANDS

special
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. 

domain
Specifies the name of the domain.

DESCRIPTION

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. 

NOTES

This command supports shorthand names for LSM volume names. For example, if you enter the following:

# chvol testdg.vol1 dom1

the volume name will be translated to:

# chvol /dev/vol/testdg/vol1 dom1

RESTRICTIONS

The values for the wblks and rblks attributes are limited by the device driver. 

You must be the root user to use this command. 

EXAMPLES

     1.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

     2.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

     3.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

     4.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

SEE ALSO

Command: showfdmn(8)

Files: advfs(4)