NAME

dfconf, dflist, dfreset − disk farms and administration

SYNOPSIS

dfconf [ −c ] ctrldev secs cnt dev ... 
dflist dev [ dev ... ]
dfreset ctrldev [ ctrldev ... ]

DESCRIPTION

Disk farming allows one or more disk partitions on one or more disk drives to be combined into one logical disk partition.  Each disk farm is represented by three devices: a block access device (found in /dev/farm), a raw access device (found in /dev/rfarm), and a controlling device (found in /dev/farmctrl).  The controlling device is used when configuring, resetting, or listing a farm; the raw access device can also be used to list the farm.  Once configured, the block and raw devices behave as any other disk device. 

Each disk partition in the farm is divided into one or more equal sized groups of logically consecutive sectors called leaves.  A farm is arranged such that sectors 0 through N-1 map to the 0th leaf of the first partition, sectors N through 2N-1 map to the 0th leaf of the second partition, etc., each disk in turn contributing the next block of N sectors.  Each partition contributes the same number of leaves, and all leaves are the same number of sectors. 

dfconf configures a disk farm for use.  If −c is the first argument, the disk farm configuration will be listed after a successful completion.  ctrldev must be the /dev/farmctrl corresponding to the farm to be configured.  secs is how many sectors (NBPSCTR bytes per sector) in a leaf.  The only logical constraint on this number is that the number of bytes in a leaf must be a multiple of the access size.  For example, if the farm will be read and written in 4Kbyte pieces, secs must be a multiple of (4K/NBPSCTR).  cnt is the total number of leaves contributed by each partition.  The remaining arguments are the block special device file(s) which make up the farm. 

N.B.  No checking is done during configuration, so it is possible to have a successful configuration and not be able to use the farm. 

dfreset clears the state of the named farm(s), as in preparation for system shutdown or to reconfigure a farm.  The specified device(s) must be the /dev/farmctrl corresponding to the farm to be reset.  If the farm is currently open by a process or mounted, the reset will fail. 

dflist lists the configuration for the named farm(s).  The specified device(s) may be either the corresponding /dev/farmctrl entry or the appropriate /dev/rfarm character special file. 

Both dfconf and dfreset may only be invoked by the super user.  dflist may be invoked by any user, provided they also have read/write permission for the necessary farm device(s). 

September 02, 1992