Alan Brown schrieb:
> On Thu, 13 Aug 2009, Ralf Gross wrote:
> 
> > I just had a bunch of 40 LTO-4 tapes that had problems during backups
> > (or worse -  only during the verify job afterwards). All from the same
> > production date. So my trust in tapes is not that good anymore...
> 
> What do the SMART stats from those tapes look like?

smartctl showed different error. Most of the time we saw media errors
in syslog during backup. Our vendor used VeriTape
(http://www.mptapes.com/) to check the tapes. They had a "VeriScore"
from 5-10 points out of 100 (many servo errors...).

The L&TT tool from HP also showed the tapes as bad in the drives
history.

Getting the information about tape errors and status from the L&TT
tool (or any other way) into bacula would be cool.

It's really a pity that this information is not easy to get and to
integrate in bacula. Even our Overland changer doesen't show this
detailed information.


> LTO has separate read and write heads.
> 
> The technology verifies what's been written a few ms after it's been
> written and the drive will rewrite any data blocks it decides has
> uncorrectable errors in.


The affected LTO tapes were marked as full after less than 800 GB, so
there were too many blocks that had to be rewritten....

 
> If the SMART stats look ok then the problem is likely your HBA or f/c
> interfaces (too short a FC cable can cause all sorts of wierd problems..)

The tapes werde bad. But recently I had a bad LTO-4 drive too. I hate
Murphy. The drive was writing perfectly with ~120 MB/s for 10-20 GB,
but then dropped to 30-40 MB/s. In the end an assessment test with the
L&TT tool showed that the drive had problems to keep the track.

L&TT is a really helpful tool.

Ralf

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