Exabyte warnings, write retries

[Craig Bishop]

katz at rpal.com writes:

>In article <1990Oct7.214035.20639 at rice.edu> lbd at alux4.att.com writes:

>> We have a 4/490 running 4.1, on which we run incremental and full dumps.
>> The dumps all seem to run just fine, but we get repeated warnings:
>> 
>> Aug 28 13:35:49 latin1 vmunix: st1:  warning, the tape may be wearing out or
>> Aug 28 13:35:49 latin1 vmunix:       the head may need cleaning.
>> Aug 28 13:35:49 latin1 vmunix: st1:  write retries= 1135 (60.3%), file= 0, block= 1880
>> 
>> The number of retries is usually in the same range, but the percentage of
>> retries varies, from 6% to 80%.  I realize that this is a warning, so it's
>> not hurting my dumps, but it is a pita, and my messages files fill up
>> awfully fast.

>You have found a bug in OS4.1.  There is a patch available.  The following
>is from the README of the patch tape:

>Premature "st?: warning tape may be wearing out or...." caused by high
>soft error rate at the beginning of new 8mm video tape.  Exabyte's Exatape
>does not seem to have this problem.

We found this not to be entirely true. The error would occur not only at
the start of a tape but all the way through as well. Sun is looking into a
problem with the manipulation of Exabyte tape units since the introduction
of SunOS 4.1 which seems to result in the tape being positioned badly.

It is interesting to note that the tape is positioned in different places
depending on whether it has just been placed in the drive or it has just
been rewound. We noticed this because PC-Lifeline will full over (since
SunOS 4.1) in different places depending on which of the above has
happened.