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Date:      Sat, 04 Dec 1999 19:30:19 +1000
From:      Stephen McKay <syssgm@detir.qld.gov.au>
To:        mjacob@feral.com
Cc:        freebsd-scsi@FreeBSD.ORG, syssgm@detir.qld.gov.au
Subject:   Re: Tape driver problems 
Message-ID:  <199912040930.TAA02368@nymph.detir.qld.gov.au>
In-Reply-To: <Pine.BSF.4.10.9912022155061.23244-100000@beppo.feral.com> from Matthew Jacob at "Thu, 02 Dec 1999 22:17:05 -0800"
References:  <Pine.BSF.4.10.9912022155061.23244-100000@beppo.feral.com>

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On Thursday, 2nd December 1999, Matthew Jacob wrote:

>> On Thursday, 2nd December 1999, Matthew Jacob wrote:
>> 
>> >> mt: /dev/nrsa0: Device not configured

>[Extra errno values and how solaris does it]
>Well, send-pr it as an RFE. It'll be a post 4.0 thingie tho.

I'll put something together if not beaten to it.

>> >I'll have to check what happened here. Do you have CAMDEBUG defined?
>> 
>> Hmm.  That looks like the sort of thing I might do. ;-)  I'll confirm
>> tonight to see if this is my fault.

I have INVARIANTS and INVARIANT_SUPPORT but not CAMDEBUG.  I've not tried
the post-1.39 versions yet, so you've probably fixed this.

>Try and change the MAXPHYS sizes in samount to 8192. I've done this to see
>what happens (not really sure yet whether it works as well as I'd like).

I tried using MAXPHYS, 64K and 8192.  I tried a blank tape (fresh from
the wrapper) and 2 tapes already written at 2GB and 5GB density with a
32KB blocksize.  MAXPHYS caused the "too many segs" error.  The others
didn't cause any errors.  Further, a kernel from mid November did not
correctly determine the initial density.

The intriguing thing is that all 3 gave the correct density for each tape.
From this I concluded that the fake read was unnecessary.  I tried with
the read commented out and it still works.  (I left in the rewind and
other stuff.)  So, for my equipment at least, some other recent change
has produced the improved density detection.

Also, the extra read is not free.  It adds an extra 30 seconds to the
startup time.  It takes about 40 seconds from tape insertion to ready,
then the density determining read adds 30 seconds.  Before this patch, an
initial read starts after about 6 seconds.  Now it takes about 36 seconds.

Well, I'm off to test the new changes.  I let you know if I learn anything.

Stephen.


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