Content-type: text/html Man page of chvol

chvol

Section: Maintenance Commands (8)
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NAME

chvol - changes the attributes of a volume  

SYNOPSIS

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


 

OPTIONS

Specifies the maximum number of 512-byte blocks that the file system reads from the disk at one time. Specifies the maximum number of dirty, 512-byte blocks that the file system will cache in-memory (per volume in a domain). Dirty means that the data has been written by the application but the file system has cached it in memory so it has not yet been written to disk.

The number of blocks must be in multiples of 16. The valid range is 0-32768. The default (when a volume is added to a domain) is 768 blocks. For optimal performance, specify blocks in multiples of wblks (as specified by the -w option). Specifies the maximum number of 512-byte blocks that the file system writes to the disk at one time. Turns I/O consolidation mode on or off. Activates a volume after an incomplete rmvol operation.
 

OPERANDS

Specifies the block special device name, such as /dev/rz2c. Specifies the name of the file domain.
 

DESCRIPTION

The chvol command enables you to change the attributes of a volume in an active domain. For example, the file system can consolidate a number of I/O transfers into a single, large I/O transfer. The larger the I/O transfer, the better the file-system performance. If you attempt to change the attributes of a volume in a domain that is not active, an error messages is produced.

The initial I/O transfer parameter for both reads and writes is 128 blocks. Once you change the I/O transfer parameters with the -r option or the -w option, the parameters remain fixed until you change them. 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.

For file system workloads that are heavily biased toward random writes, use the -t option to increase the file system's dirty threshold. This may improve file write performance.

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.
 

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

The following example displays the cmode and the I/O transfer parameters of the /dev/rz1c volume in the domain1 file domain: # chvol /dev/rz1c domain1 rblks = 128 wblks = 128 cmode = on The example also toggles the cmode: # chvol -c off /dev/rz1c domain1 # chvol /dev/rz1c domain1 rblks = 128 wblks = 128 cmode = off The 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/rz1c domain1 # chvol /dev/rz1c domain1 rblks = 256 wblks = 256 cmode = on


 

SEE ALSO

advfs(4), showfdmn(8)


 

Index

NAME
SYNOPSIS
OPTIONS
OPERANDS
DESCRIPTION
RESTRICTIONS
EXAMPLES
SEE ALSO

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Time: 02:40:43 GMT, October 02, 2010