Re: Questions about multi-device behavior

[Hugo Mills <hugo@carfax.org.uk>]

[-- Attachment #1: Type: text/plain, Size: 1555 bytes --]

On Thu, Jul 18, 2013 at 02:59:58PM -0700, Roger Binns wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> On 18/07/13 13:05, Chris Murphy wrote:
> > Sounds like if I have a degraded 'single' volume, I can simply cp or
> > rsync everything from that volume to another, and I'll end up with a
> > successful copy of the surviving data. True?
> 
> Not quite.  I did it with cp -a.  Because all the metadata survived, cp
> would create the target file, but then get an i/o error on opening/reading
> the source file.  It would print an error message, but not delete the
> empty target file. Consequently I ended up with loads of zero length files
> I had to go in and delete afterwards.

   The odds of having an undamaged file from that process are much
better for single than for RAID-0 (and aren't affected by having tools
which will cope better with IO errors -- although you'll get more of
each damaged file if you do). As the file size goes up, the odds of it
being damaged increase.

   Hugo.

> I briefly looked for an rsync option to keep going on source i/o errors
> but didn't find one.
> 
> Roger
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.12 (GNU/Linux)
> 
> iEYEARECAAYFAlHoZV4ACgkQmOOfHg372QRPFwCgob01TavS2qffBkxkuv0g9bl3
> pC8An25Mgx+cRXb0Kds+GRnzaj2P0Acy
> =UA5J
> -----END PGP SIGNATURE-----
> 

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
  PGP key: 65E74AC0 from wwwkeys.eu.pgp.net or http://www.carfax.org.uk
  --- I am an opera lover from planet Zog.  Take me to your lieder. ---  

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 828 bytes --]