On 02/06/2011 08:36 AM, Andreas Dilger wrote: > On 2011-02-06, at 4:49, [email protected] wrote: >> Currently, tar seems to perform quite sub-optimally when archiving sparse >> files. I compared the performance of GNU tar and star when archiving a >> large (~2TB) sparse file. All but about 180MB of the file was holes. > > There was a patch posted a while ago by Bernd Schubert to detect completely > sparse files, bit I don't know if there was anything to automatically handle > partially sparse files. > >> Sometimes it's possible to determine the exact hole layout in a file. >> Apparently that's quite easy in Solaris (SEEK_HOLE, SEEK_DATA) and >> Windows, less so in Linux (FIEMAP). > > A question to the tar maintainers - if someone were to write support for > FIEMAP detecting holes on Linux would this be acceptable to include upstream?
The patch is already in the process of being written - see coreutils 8.10. However, there are still some bugs being fleshed out, and adding support for Solaris SEEK_HOLE, before that code is migrated to gnulib and imported into tar. -- Eric Blake [email protected] +1-801-349-2682 Libvirt virtualization library http://libvirt.org
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