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chvol(8)
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
  -A  Activates a volume after an incomplete addvol or rmvol operation.

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

  -l  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.

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

  -t blocks
      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 16,384
      blocks. For optimal performance, specify blocks in multiples of wblks
      (as specified by the -w option) and multiples of rblks (as specified by
      the -r option).

  -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.

  domain
      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 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.

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 file 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
  advfs(4), showfdmn(8)

Index for Section 8

Alphabetical listing for C

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