I used to get this a lot.  And, it was always on AIT-2 tapes with weird
block sizes, on AIT-3 drives.  The drive would happily read the tape and
then wham, it encounters a part where the block size is different and
then the error comes up.  We used to have AIT-2 drives which labeled and
wrote to these tapes.  We started getting the errors after we changed
the drives to AIT-3.

We're slowly migrating off of AIT-2 tapes.  In case we do run out of
tapes and have to reuse our old AIT-2 tapes, I make sure to erase them
(write something over them using tar or mt erase) and then label them.
I read that relabeling should suffice (without erasing), but I'm
paranoid.



-----Original Message-----
From: Legato NetWorker discussion [mailto:NETWORKER AT LISTMAIL.TEMPLE DOT EDU]
On Behalf Of Davina Treiber
Sent: Tuesday, December 09, 2003 12:22 PM
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Subject: Re: [Networker] Tape Positioning by Record is Disabled on AIT
Drives??????


Dave Martini 1 wrote:
> I have Networker Server 7.1 and a Spectra Logic treefrog
> with dual Sony AIT-3 Drives running on a solaris 9 server.
>
> My st.conf entry looks like this
>
> tape-config-list=
>            "SONY SDX-700C", "SONY 8mm AIT-3 ", "SONY_AIT3";
>             SONY_AIT3=1,0x36,0,0xd679,1,0x00,0;
>
> Legato says that the syntax of my st.conf is correct for the Sony 
> AIT-3.
>
> But whenever I try to restore I get this error.
>
> "Cannot decode block. Verify the device configuration. Tape 
> positioning by record is disabled."
>
> Sometimes the recover works and sometimes the recover fails.
>
> I called Legato and they said put these two environment variables in 
> place so I put them in the .login file on the UNIX solaris 9 legato 
> server machine and rebooted
>
> setenv NSR_DEV_BLOCK_SIZE_AIT_3 192
> setenv NSR_DEV_TAPE_FILE_SIZE 10922
>
> The problem is still occuring.

A .login file is not the place, you need to put these commands in the
startup script for NetWorker, and you need to convert them to sh syntax,
i.e. VARIABLE=value; export VARIABLE The FILE_SIZE variable won't make a
scrap of difference to restores, but may affect the seek time when
backing up.

Somehow I don't think this is your problem though. If you always had the
problem then it might be, but if it is intermittent then it means one of
two things:

(1) You have a mixture of block sizes in use
(2) You have some other error which may be media or drive related, or
some other hardware problem.

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