Hello,
18.12.2009 14:38, Oliver Lehmann wrote:
> Dan Langille writes:
>
>> Have you considered that perhaps your backup is corrupted? That is, the
>> USB2 HDD that you have backed up to contains a disk error?
>>
>> I would be very careful with that HDD, whatever you do, especially if
>> that is your only backup of this data.
I agree with Dan... I see the same sort of problems relatively often
(15 times during the last 3 months), but I know *I* can accept that
fault rate.
This happens, as far as I can see, only with external drives (USB in
your and other cases, FireWire here), so I attribute it to imperfect
external disk controller chips or USB / FireWire stacks. Whenever I
saw those sort of errors on internal disks, I either get log messages
or can identify faulty disk drives using smartctl. For external disks,
this usually doesn't work. :-(
>
> I'm starting an offline SMART test now but I doubt that this will reveal
> anything. The disk has a UDMA_CRC_Error_Count of 1 but this is not that
> much. Right now I can't think that the disk has a problem. If this would
> be the case and I would access a file on a corrupt disk FreeBSD would have
> spammed my console already with read errors. Same goes for write.
>
> I'll let you know what the SMART analysis revealed.
>
> Is there a way to force bacula to re-read the backups after they where
> written or do I have to schedule continuous restores to make sure they stay
> readable?
No, none that I know. An actual restore is the only way to find this.
To make sure your restores don't fail, run the SD with '-p', and
*really close watch for those errors in the reports*.
That works for me - if I had really critical data saved only once, I'd
be worried. As it is, I use the external disks as temporary storage
and for low-priority backups, so those problems aren't really serious
here.
(Actually, this confirms my belief that most low-cost external HD
cases are hardly ever really good, and often are crap...)
Cheers,
Arno
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--
Arno Lehmann
IT-Service Lehmann
Sandstr. 6, 49080 Osnabrück
www.its-lehmann.de
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