MKDBLE(8)

NAME
mkdble - build a compressed special file

SYNOPSIS
mkdble special size [factor [encoding [block_size [cluster_size]]]]

DESCRIPTION
The mkdble command builds a compressed special device, or a file for use by the "DouBle" on-the-fly block device compression driver. special is the name of either a block device, or a regular file that will be used by the driver for compressed data storage. mkdble will create the special file if necessary. size is the size in kilobytes of the special file. factor is the minimum expected average compression factor. This depends on the compression algorithm (encoding) used and the type of data stored on the special file. Default is 2.0, but values between 1.6 and 1.8 are usually more reasonable. The behaviour of the compression driver will become unpredictable when the device is full. Therefore, lower factor values are safer. encoding Is the default compression algorithm for the compressed device. In version 0.4: 0 - means no encoding (no compression) 1 - is a modified LZW algorithm 10 - is the predictor algorithm 11 - is the LZV algorithm (default) 12 - is the LZRW2 algorithm 13 - is the LZRW3A algorithm In versions < 0.3, LZV, LZRW2 and LZRW3A used to have codes 102, 212 and 312 respectively. Versions 0.3 and 0.4 are backward compatible, but do not use these values unless you know what you're doing. block_size Is the size of blocks ( must be 2^n with n > 7 and n < 11). The best compression is usually achieved with 256 bytes (n=8), the best speed is obtained with 1024 bytes (n=10). Default is 512 bytes (n=9). cluster_size Is the size of clusters (n*block_size, but at most 10240 bytes). The best compression is usually achieved with 10240 bytes, but compression is faster with 4096 bytes. Default is currently 10240 bytes. There will be no compression unless cluster_size >= 2*block_size.

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

AUTHORS
Jean-Marc Verbavatz <jmv@achaz.saclay.cea.fr> LZV was written by Hermann Vogt <herm@pirx.han.de> LZRW* was written by Ross Williams predictor was written by Dave Rand and last modified by Peter Trattler

DISCLAIMER
All the compression algorithms are patented in some countries. For more information, refer to the compression FAQ, posted regularly on "comp.compression".