In order for the DLT7000 to perform
a fast locate the directory on the tape
must be intact.

If the directory is not intact, it has no
choice but to read over the tape until it
reaches the position.

I suspect you have tapes with corrupt
directories hence why the drive says
reading.

Best to call out your tape vendor to
rebuild the directories on the tapes
using specialised software.

The directory on tapes can get corrupt
for many reasons. The most common
is powering off the drive with a tape
in it that has not been offlined.

This is a common problem with the DLT format.
Tape technology such as the 9840 do not have
this problem, since the drive is able to
rebuild the (MIR) directory in real-time.

Regards
Peter Marelas


-----Original Message-----
From: alex canady [mailto:acanady AT yahoo DOT com]
Sent: Wednesday, 24 October 2001 12:00 AM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] slow tape positioning/seeking


greetings

we run NB datacenter 3.4 on solaris and a sun L280
library that contains a DLT7000 drive.  tape
positioning seems extraordinarily slow.  having no
prior experience with this drive i was unsure if i
simply had unreasonable expectations however both
veritas and sun have told me that the positioning
times i'm getting is abnormal.

it can take between 1-3 hours to position to various
positions on the tape. it is consistent (it takes the
same amount of time to position to the same file
number on the same tape).  all tapes exhibit this
behaviour, new tapes and recycled tapes.  it is also
the same whether veritas positions the tape or whether
one does so manually with mt commands (the same amount
of time with either).  when the tape is positioning
the LEDs on the front of the library displays
'READING'.  

i have had a case open with Veritas and now a case
open with SUN for several weeks.  i have updated
st.conf, applied the latest st driver patches,
upgraded to the latest patch of nb datacenter, etc.,
... we have checked to see if veritas was in 'fixed
block' vs 'variable block' mode and we are fairly
certain it's correctly in variable mode.  i'm using
/dev/rmt/0cbn device.  sun/veritas seem to think this
is fine.   sun has indicated i the firmware is fine.


if anyone has any ideas i would muchly appreciate the
input.

thanks,

alex
acanady AT yahoo DOT com



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