[GRASS-dev] GRASS raster compression & performance

[Markus Neteler]

(back to an older question)

On Sun, Dec 11, 2011 at 10:39 PM, Markus Neteler <neteler at osgeo.org> wrote:
> Hi,
>
> since my office grassdata/ becomes huge, I wonder if I should
> change to zlib compression.
>
> From the "variables.html" page I get (btw: no mention of this in
> the r.compress manual!):

I have now updated the manual page.

> GRASS_INT_ZLIB
>     [libgis]
>     if the environment variable GRASS_INT_ZLIB exists, new compressed
> rasters will be compressed using zlib instead of RLE compression. Such
> rasters will have a compressed value of 2 in the cellhd file.
>     Obviously, decompression is controlled by the raster's compressed
> value, not the environment variable.
>
> I wonder what the performance penalty of zlib could be. Does
> anyone have experience? An advantage of stronger compression
> could be that the data traffic on NFS on a cluster becomes less...
>
> Opinions welcome,
> Markus

Meanwhile I discovered the .xz file format:
http://en.wikipedia.org/wiki/Xz
http://tukaani.org/xz/format.html

Maybe worth to be implemented in GRASS?

Markus