DBFRAG(8)

NAME
dbfrag - check fragmentation of a "DouBle" compressed block device

SYNOPSIS
dbfrag [-v[v]] special

OPTIONS
-v: more verbose

DESCRIPTION
dbfrag is used to check fragmentation on a compressed block device. special is a compressed block device or file, created by the mkdble command. dbfrag will report: - cluster fragmentation and average 1024-byte block gap between clusters. This value is not as critical as the two others, but should be as small as possible. - block fragmentation within clusters and average 1024-byte gap between blocks. This value should be as small as possible... - Average cluster deviation, which measures the average distance between the actual location of a cluster and its ideal position. This value is heavily dependent on the difference between actual compression and the value given as a argument to mkdble. As far as performance goes, the most important value is, by far, block fragmentation. Until version 0.4 of "DouBle", no effort had been made to prevent fragmentation. Blocks were essentially allocated as close as possible to the beginnning of the device. In version 0.4a, block allocation has been changed in order for block layout to follow cluster layout as closely as possible. This will probably result in higher cluster fragmentation, but smaller block fragmentation and cluster deviation - blocks should be allocated closer to where they should be, but gaps between clusters will be more frequent.

BUGS
There is currently no defrag utility :( - dbfrag is only intended to see fragmentation change with time and/or driver versions. Comments are welcome !

SEE ALSO
dbmount(8),dbumount(8),mkdble(8),dbck(8)

AUTHORS
Jean-Marc Verbavatz <jmv@achaz.saclay.cea.fr>