Re: [gentoo-user] Re: [OT] filesystems

[Shawn Haggett <podge@podgeweb.com>]

On Sat, 29 Nov 2008 04:21:44 pm Jorge Peixoto de Morais Neto wrote:
> On Thu, Nov 27, 2008 at 10:12 AM, Daniel Troeder <daniel@admin-box.com> 
wrote:
> > Am Mittwoch, den 26.11.2008, 15:26 +0100 schrieb Florian Philipp:
> > You can buy so called "archival grade" DVD-Rs that should work for 10-20
> > years in a good environment. There are hugh differences between
> > products. In germany you can buy very good ones from Verbatim for around
> > 2€/disk.
>
> This can be hard to find in my mid-sized Brazilian city. If I lived in
> the mega-metropolis of São Paulo, this would be far easier. And thanks
> very much for recommending Verbatim. I have heard of Taiyo Yuden, but
> that would likely be far harder to find.
>
> Speaking of md5sum/shasum, do you know some tool that adds data
> redundancy? I heard dvddistaster does this, but I guess it is limited
> to DVDs. It would be great fo find a general data redundancy tool. In
> the moment, with the tools I know, the best I can do is store the
> files twice, with md5sums/shasums to decide which version is correct.

Have a look at app-arch/par2cmdline ( http://parchive.sourceforge.net/ ). It 
will create parity files for an arbitrary set of data files and you can 
choose your level of redundency (from 0 = now redundency, just integrity 
checking, up to 100%). Although expect your parity files to be on the order 
of the percentage for size, i.e. 50% redundancy for some given files to take 
about 50% of their size for the parity files).

The down side I find with the tool is that it doesn't currently support 
directories. This isn't so bad for creating parity files, but during 
checking/restore, the program expects all files to exist in the current 
directory, despite which sub-dirs they were originally in. You can get around 
this with a tar/rar/zip first, then calculate parities on the archive though.

> By the way, it seems from my (limited) experience that even sha256sums
> are IO-bound (even on my not-so-powerful Athlon XP 2600+), so it makes
> sense to calculate sha256sums (as instead of md5sums) even it is
> overkill. To be doubly sure, one can calculate sha256sums *and*
> md5sums.