Date: Wed, 12 Mar 1997 12:50:01 -0800 (PST) From: Stefan Esser <se@freebsd.org> To: freebsd-bugs Subject: Re: kern/2965: st0 hang/fail on reading 4mm DAT tape for larger files Message-ID: <199703122050.MAA10436@freefall.freebsd.org>
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The following reply was made to PR kern/2965; it has been noted by GNATS.
From: Stefan Esser <se@freebsd.org>
To: jin@iss-p1.lbl.gov
Cc: FreeBSD-gnats-submit@freebsd.org
Subject: Re: kern/2965: st0 hang/fail on reading 4mm DAT tape for larger files
Date: Wed, 12 Mar 1997 21:42:40 +0100
On Mar 12, "Jin Guojun[ITG]" <jin@iss-p1.lbl.gov> wrote:
> >Synopsis: st0 hang/fail on reading 4mm DAT tape for larger files
> 2.2-SNAP(s) with HP C1536A SCSI 4mm DAT tape drive:
> (ncr0:4:0): "HP HP35480A T503" type 1 removable SCSI 2
> st0(ncr0:4:0): Sequential-Access
> st0(ncr0:4:0): 5.0 MB/s (200 ns, offset 8)
>
> >Description:
>
> tar -c some.files # writing OK
> tar -t
> or
> tar -xv
> will hang when looking/reading a file larger than about 6090 Bytes;
>
> tar: read error on /dev/nrst0 : Input/output error
>
> tar process is hanging at here and tape drive stopped.
>
> system errors:
> ncr0:4: ERROR (0:48) (1-21-1e) (88/13) @ (c2c:19000200).
The error code (0x48) signals a GROSS ERROR, which in most
cases is an over- or underflow on the SCSI bus while doing
a synchronous transfer. This means, that either one byte
has been acknowledged null or two times.
This is a reported hardware error.
> script cmd = 89030000
> reg: da 10 80 13 47 88 04 1f 01 01 84 21 80 01 99 00.
> ncr0: have to clear fifos.
> ncr0: restart (fatal error).
> st0(ncr0:4:0): COMMAND FAILED (9 ff) @f2136c00.
> ncr0: timeout ccb=f2136c00 (skip)
>
> The tar process cannot be killed. The only solution is power
> cycle the tape drive.
>
> The same hardware worked with 2.1.{6-7} without any problem.
> So, it looks like software problem in the kernel somewhere.
Well, it looks like the error recovery fails, and there
is actually a difference between 2.1 and 2.2, but with
2.2 surviving a number of scenarios where 2.1 hung.
I know that the error recovery code needs quite some work,
but the primary cause of your problem is more likely
related to a SCSI bus problem, which is only visible by
the failed recovery procedure.
I'm using a HP1533A DDS-2 DAT drive for my backups and
to exchange data, and never had a single occurance of a
hang under any -current (i.e. post 2.1 kernel).
Please make sure that there is no problem with your
controller or SCSI bus cable/terminators/terminator
power ...
Regards, STefan
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