[CentOS] block level changes at the file system level?

Mon Jul 7 12:35:47 UTC 2014
SilverTip257 <silvertip257 at gmail.com>

On Thu, Jul 3, 2014 at 4:50 PM, Ljubomir Ljubojevic <centos at plnet.rs> wrote:

>
> > Whatever we do, we need the ability to create a point-in-time history.
> > We commonly use our archival dumps for audit, testing, and debugging
> > purposes. I don't think PG + WAL provides this type of capability. So at
> > the moment we're down to:
> >
> > A) run PG on a ZFS partition and snapshot ZFS.
> > B) Keep making dumps (as now) and use lots of disk space.
> > C) Cook something new and magical using diff, rdiff-backup, or related
> > tools.
> >
>
> Check out 7z from p7zip package. I use command:
>
> 7za a -t7z $YearNum-$MonthNum.7z -i at include.lst -mx$CompressionMetod
> -mmt$ThreadNumber -mtc=on
>

Seems to be that 7zip uses LZMA for the 7z archives (though it supports
other compression types).  Confirmed below.


>
> for compressing a lot of similar files from sysinfo and kernel.log,
> files backuped every hour that do not change much. And I find out that
> it reuses already existing blocks/hashes/whatever and I guess just
> reference them with a pointer instead of storing them again.
>
>
> So, 742 files that uncompressed have 179 MB, compressed ocupy only 452
> KB, which is only 0.2% of original size, 442 TIMES smaller :
>
> Listing archive: 2014-03.7z
>
> --
> Path = 2014-03.7z
> Type = 7z
> Method = LZMA
>

Exactly ... LZMA ...
Grab the "xz" package for CentOS 6

There's also an --lzma option for tar.

I am inclined to use xz utils as opposed to 7zip since 7zip comes from a
3rd party repo.

-- 
---~~.~~---
Mike
//  SilverTip257  //