Dumping of large LMFS

[MMcM@TITANIA.Oberon.COM (Mike McMahon)]

    Date: Thu, 23 Jan 92 10:51:38 -0500
    From: lisar@nynexst.com

    I have a 3650 with more than a gigabyte of LMFS.  As you might
    imagine, backing up the system is a pain.  On the same network
    I have an XL400 with an exabyte.  I can make carry-tapes and
    dumps of the 3650 on the exabyte, but I seem to encounter the
    end of the tape long before I should.

When you perform the backup, does it say that it is using the 7.2 format
or the default format?

The older backup format puts a tape mark between each file.  On a
helical scan device like the 8mm exabyte, a tape mark uses about as much
tape as a 1MB file.  As you can see, that only allows a couple thousand
files per tape.

I am not entirely sure why it would be using the older format, but
that's something to check.

    Date: Thu, 23 Jan 92 17:43:40 EST
    From: gensym!mhd@harvard.harvard.edu (Mark H David)

    Does anyone know of either an RTAPE driver for the SPARC or an RMT
    protocol implementation (which the SPARC does support) for a 3620?

The UX-Support system includes a RMT user side.

If you want to back up a large LMFS to Exabyte, things are a little
stickier.

Because of all the buffering that exists between the RMT client and the
actual tape, when Genera sees an end-of-tape exception from the Unix
server, it does not actually know how many files (just bytes in the new
format) were written successfully.  For this reason, Genera does not
allow backup in the newer format, but only in the 7.2 tape-mark-per-file
(where it can know) format.

Now, of course, if you're willing to promise that you won't get an
end-of-tape (which is reasonable, since a 120 min tape holds 2.2GB), you
can patch the RMT client to claim to support the necessary position
query messages.  Symbolics support ought to be able to give you this
patch.  (I think the usual cautions apply to my doing so.)

If your Sun is running 4.1.1, there's another complication.  SCSI tape
is broken in that release.  You will get a kernel panic when Genera asks
the RMT server to rewind the tape.  You need patch 100280-02 for the
Sun.  (I don't know whether I'm allowed to give this to you patch.  Does
anyone else know?)  [Now this patch, which is actually the eighth in a
series of released attempts to fix the problem, isn't perfect either.
If you do mt offline, the Sun will spit out the next tape you try to
insert immediately; several tries will be necessary to get one loaded.
Also, when doing a Compare Backup from Genera, it will somehow manage to
keep rewinding and seeing the same tape over and over again.  In any
case, these problems are much less bothersome than panics.]

We back up our LMFS to an Exabyte on a Sun file server.  It was a bit of
a nuisance setting it up, but the time and money we've saved over QIC
has definitely made up for it.