Solution for "Unexpected busfree in Message-out phase" while using a scsi tape streamer

[Friedrich Lobenstock <fl@fl.priv.at>]

Hi!

I keep getting questions about how I fixed the problem to my orginal
posting to this list. A reference to my posting is here:
   http://groups.google.com/groups?q=author:fl%40fl.priv.at&hl=en&lr=&ie=UTF-8&client=googlet&selm=linux.scsi.3CF1F492.6060300%40fl.priv.at&rnum=6

The solution is to use a fixed blocksize. LTO tape streamers need a fixed blocksize
of 1K and DLT ones runs best with 8 to 64k. BUT there's somehow a barrier at 8k, see:
   http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&client=googlet&selm=3D77B216.8070205%40fl.priv.at

For AIT I don't know, but you might want to experiment with the blocksize to
find out which is best for AIT.

BUT I can only speak about using LTO or DLT with ARKEIA Version 4.x
(http://www.arkeia.com/). Someone with the same LTO problem kindly
forwarded me the mail you can find below. Later I applied it to DLT
and it worked too.

So this mostly applies to ARKEIA, but it might work with your backup solution
too.

Greetings
Friedrich Lobenstock

-------- Original Message --------
Subject: Antwort: Re: Linux Problem SCSI Laufwerk HP Ultrium
Date: Mon, 24 Jun 2002 12:17:02 +0200
From: <...email deleted for anonymity...>
To: Friedrich Lobenstock <fl@fl.priv.at>


Hallo Friedrich,

bei uns läuft's jetzt nachdem wir die unten stehende Antwort vom Arkeia
Support erhalten hatten.....


Thomas,

The HP Ultrium LTO (particularly your model 215) works better when
configured with a 1024 tape block size (the default is variable
block size). Arkeia provides a way to force the tape block size:

In /usr/knox/arkeia/arkeia.prf file create the preference:

         ARK_SET_BLKSIZE "1"

and in the file /usr/knox/arkeia/dbase/f3drv/drvtypes.lst add the
SET_BLKSIZE property
into the LTO drive type as following:

         ITEM    {
                 "NAME"  "LTO"
                 "FORM_FACTOR"   "LTO"
                 "TIME_BEFORE_CLEAN"     "40"
                 "SET_BLKSIZE"    "1024"
         }

You have to restart Arkeia (both the graphic interface and NLSERVD) to be
sure the new configuration is take in count. Please note that after this
change Arkeia will not read the tape created previously with the variable
block size.

How To Migrate The Existing Tapes:

After setting the 1024 tape block size, Arkeia cannot restore from tapes
made by using the default variable tape block size. So we need a procedure
to migrate...
After changing the Arkeia configuration, delete all free tape definitions.
Re-create the tapes with a new basename and re-label them to be sure Arkeia
can work with these tapes.
If the Arkeia restoration asks for an old tape (just check the name), come
back to the old configuration, stop and restart the Arkeia GUI and perform
the restoration.

Let me know if this help you.

Michel Tugaye



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