chvol(8)						      System Manager's Manual							  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.  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).  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.  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

       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 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
       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	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)

																	  chvol(8)