I'm having problems writing to tapes in my DELL PV124T tape library,
which has been running fine for 6 months or so (it is second hand and
about 2 years old). It is connected via a SAS HBA on a Linux Debian
machine running a 2.6.33-2-amd64 custom compiled kernel to support the
mvsas module.

(boot messages:
    ... scsi 1:0:1:0: Sequential-Access QUANTUM  ULTRIUM 4        2210 PQ: 0 
ANSI: 5
    ... st 1:0:1:0: Attached scsi tape st0
    ... st 1:0:1:0: st0: try direct i/o: yes (alignment 4 B)
    ... st 1:0:1:0: Attached scsi generic sg3 type 1
)

I'm running Bacula in a single-host only arrangement. Bacula is patched
(in response to a dare from Dan Langille) version of 5.0.2 to support
batch inserts.

Normally I can write to tape at around 100MB/s with hardware
compression enabled.

I've recently put in a set of new tapes, and cleaned the tape head. Two
attempts at a roughly 8 tape backup have failed on the 2nd or 3rd tapes. I've
reset all the tapes by rewinding and writing WEOF but the error is
persistent.

Fixing this problem is somewhat complicated by the fact that the tape
library is in a rack in our data centre. Consequently I've run 'btape
fill' over the first 4 tapes in the library, with the following results:

    tape 1 : fine, but ran at about 55MB/s
    tape 2 : failed after a few 100GB
    tape 3 : failed after a few 100GB
    tape 4 : failed after hours of running at only 10MB/s

The failures are announced with the following error message:
JobId 0: Fatal error: Unable to write EOF. ERR=dev.c:1745 ioctl MTWEOF
    error on "LTO4-Drive1" (/dev/nst0). ERR=Input/output error.

The failures are concurrent with the following kernel messages:

    kernel: [212500.667965] st0: Sense Key : Medium Error [current]
    kernel: [212500.667971] Info fld=0x0
    kernel: [212500.667973] st0: Add. Sense: Write error
    kernel: [212595.537383] st0: Sense Key : Medium Error [current]
    kernel: [212595.537389] st0: Add. Sense: Write error

I'd be very grateful for some advice about what might be going wrong.

Thanks
Rory


-- 
Rory Campbell-Lange
rory AT campbell-lange DOT net

Campbell-Lange Workshop
www.campbell-lange.net
0207 6311 555
3 Tottenham Street London W1T 2AF
Registered in England No. 04551928

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