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chvol(8)							      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
       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.

OPERANDS
       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.

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 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‐
       ume.

       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	 exam‐
       ple, 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
       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

SEE ALSO
       Command: showfdmn(8)

       Files: advfs(4)

								      chvol(8)
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