NAME

cfst, cfsd − composite file system transfer procedure

SYNOPSIS

cfst model [delay]

cfsd model [delay]

DESCRIPTION

cfst is a command procedure used to transfer files to jukebox volumes in a composite file system.  model is the model directory of a composite file system (see cfs(4)).  delay optionally specifies the transfer latency interval in minutes.  The default transfer latency interval is thirty minutes for cfst and five hours for cfsd.

The procedure interprets the CFS audit log file to discover recent modifications in the model and performs analogous changes on the jukebox volumes comprising the composite file system.  In the process, it accesses and updates data in the CFS index map file and one or more of the tally files in the CFS tally directory.  The index map file identifies every directory in the model with its index node (inode) number.  This map is needed to interpret audit log entries.  Files in the tally directory are named with the index node (inode) numbers of directories in the model and identify jukebox volumes where instances of each directory reside.  The tally is used to select volumes to accept files. 

When preparing to move a file from the model to the jukebox, the file transfer procedure selects a volume in the jukebox which already contains files in the same model directory as the file to be transferred, if one exists with enough space to hold the file; if not, it widens its search to incompass volumes containing portions of the parent of that directory, then its parent, and so on until a suitable volume is found.  This method tends to group files with similar paths together on the same volumes, and keeps files with divergent paths separated on different volumes. 

If several volumes are identified at any step, the one with the most space is chosen.  If no volume is found with enough space to accomodate a file, an interlock is set to prevent additional files being accepted, and the transfer process delays until another volume is included (see cfsi(8)).  Once a volume is identified, the file is copied to the volume and its place in the model is taken by a link to the copy. 

If the procedure is invoked using the name cfsd, it will run as a daemon, sleeping until files become eligible for transfer.  Otherwise, it will terminate once all eligible files in the model have been transferred.

FILES

model/.= directory index map

model/.:/<index> per-directory tally

model/.#/<index> transparent "alias"

model/.%/<index> duplicate file link

model/.@ operation audit log

model/.~ temporary audit log

model/.! creation interlock

SEE ALSO

cfs(4), cfsi(8), cfse(8), cmount(8)

  —  30 September 1992