Tape wearing out on Exabyte?

[Craig Bishop]

dave at imax.com (Dave Martindale) writes:

>In article <1990Aug15.235722.7639 at rice.edu> grant at saturn.cs.swin.oz.au (Grant Collins) writes:
>>I have a brand new Exabyte with a brand new tape in it and everytime I do
>>a dump over the network to it it gives a message like:
>>
>>st1: warning, the tape may be wearing out or the head may need cleaning.
>>st1: write retries= 13936, file= 0, block= 3448
>>
>>I have seen this discussed a while ago but I cant recall the
>>cause/solution to the problem.  Any ideas?   When I restore the contents
>>to an unused partition all APPEARS OK.  Is there anyway to verify that
>>nothing has been corrupted or do I just cross my fingers and hope for the
>>best?  Any help much appreciated..

>Exabytes normally get a certain number of retries when writing or reading
>a tape.  If you want to know how many have occurred on the current tape at
>any point, do a "mt status" on the drive.

In SUNOS 4.1 the st driver has changed and these errors are occurring more
frequently and erroneously.

We have a SUN supplied exabyte and as well as using it for nightly backups
we do backups of our PC's to it during the day using PCNFS Lifeline and
some control software we wrote.

Since SUNOS 4.1 we have been getting errors on our nightly saves which we
never got before and the PC backups don't work at all the PC Lifeline just
craps out.

What is happening we found was that the st driver no longer positions the
tape correctly when the tape is loaded or when it is rewound. The UNIX
tools continue to work but the errors above (we believe) are caused by
this problem.

The first PC to try and backup after the tape has been loaded fails in a
different place than the first PC save after a rewind.  PC Lifeline times
out 4 times (hard coded limit) and then gives up on the dd process running
on the Sun, the dd is not responding because it is waiting for the st
driver which is playing with the tape trying to get ready to write.

SUN Australia has reported this as a bug to SUN US and we are waiting for
a fix. We beleive the fix will stop the majority of the over night errors.

Craig Bishop			Geelong & District Water Board
Phone: +61 52 262506		61-67 Ryrie St Geelong
Fax:   +61 52 218236		Victoria 3220 Australia