misc/144043: USB DLT tape drive throws random errors

Kirk Strauser kirk at daycos.com
Wed Feb 17 16:10:05 UTC 2010

>Number:         144043
>Category:       misc
>Synopsis:       USB DLT tape drive throws random errors
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Feb 17 16:10:05 UTC 2010
>Originator:     Kirk Strauser
>Release:        8-STABLE
FreeBSD jail2.daycos.com 8.0-STABLE FreeBSD 8.0-STABLE #3: Sat Feb 13 11:03:18 CST 2010     root at jail2.daycos.com:/usr/obj/usr/src/sys/GENERIC  amd64

I have a Dell PowerEdge SC1425 server with a USB tape drive. From dmesg:

umass0:0:0:-1: Attached to scbus0
sa0 at umass-sim0 bus 0 scbus0 target 0 lun 0
sa0: <QUANTUM DLT-V4 0A00> Removable Sequential Access SCSI-2 device
sa0: 40.000MB/s transfers

The problem is that it randomly throws tape errors during writes:

# dd if=/dev/zero of=/dev/sa0 bs=1m
dd: /dev/sa0: Input/output error
3272+0 records in
3271+0 records out
3429892096 bytes transferred in 136.946745 secs (25045444 bytes/sec)

# dmesg | tail
(sa0:umass-sim0:0:0:0): failed to write terminating filemark(s)

This doesn't happen *every* time, but often enough that Amanda backups fail regularly and I'm getting nervous about what would happen if I had to explain this all to my boss.

To rule out hardware failure, I've repeated the experiment with identical tape drive units, different USB cables, different USB ports, and both used and new tapes.  Basically, writes to that model of tape drive connected to that server will fail about half the time.

This is a production server, but I can run any requested tests at night if need be.



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