On 08/11/15 13:52, Andrey Tataranovich wrote:
> On Tue, 11 Aug 2015 15:47:40 +0100
> Martin Simmons <martin AT lispworks DOT com> wrote:
> 
>> You could use bls -j with the volume file to scan the whole volume.
>>
>> I recomend use a more secure fileserver to store your backups (RAID,
>> or ZFS).
> 
> This error has happened on mirror raid, so maybe only filesystems
> like zfs/btrfs could solve such problem on system level. I do not
> remember if raid5/6 protect from situation when disk read operation
> return incorrect data without error.

All conventional RAID5/6 implementations that are not copy-on-write and
do not feature periodic scrubbing are potentially vulnerable to silent
disk corruption, aka the "RAID5 write hole".  ZFS is the only RAID
implementation which I know to be not vulnerable to this potential
failure mode.  https://btrfs.wiki.kernel.org/index.php/RAID56 confirms
that btrfs RAID5/6 is still vulnerable to the RAID5 write hole.  btrfs
also cannot yet recover data from parity, and suffers badly from
fragmentation.  The honest truth is that btrfs is still an experimental
filesystem that is not nearly stable enough or mature enough for
production use yet, much less for backup storage which absolutely MUST
be reliable.


-- 
  Phil Stracchino
  Babylon Communications
  phils AT caerllewys DOT net
  phil AT co.ordinate DOT org
  Landline: 603.293.8485

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