Hello,

I met some problem with SL55 when I tried to read the data from SCSI tape.

====================
# tar -t --blocking-factor=2048 --file=/dev/st0l
tar: /dev/st0l: Cannot read: Device or resource busy
tar: At beginning of tape, quitting now
tar: Error is not recoverable: exiting now
====================

It was quite surprising because a couple of days ago everything was 
running well.

I did

===========================
service xend restart
===========================

and after everything became fine.


Unfortunately several days later I met exactly same problem.


I tested dd

=========================
# dd if=/dev/nst0l of=test-tape count=1
dd: reading `/dev/nst0l': Cannot allocate memory
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.052914 seconds, 0.0 kB/s
=========================

and when I set right block size I see

=================================
# dd if=/dev/nst0l of=test-tape bs=1048576 count=1
dd: reading `/dev/nst0l': Device or resource busy
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.000933 seconds, 0.0 kB/s
=================================

The commands 'fuser' and 'lsof' gave nothing (no process uses this 
device).


My colleagues reminded me that in the past one of them solved such the 
issue by reboot. I do not think that reboot is good idea for the server in 
production and continue the investigation.


The man page for driver 'st' (driver for SCSI tape drive) tells

=========================
EBUSY         The device is already in use or the driver was unable to
allocate a buffer.
=========================



The main memory is quite busy

===========================
# free
              total       used       free     shared    buffers     cached
Mem:       2097152    2087972       9180          0      68624     387956
-/+ buffers/cache:    1631392     465760
Swap:      8193064        652    8192412
===========================

I did 
==================================
# echo 2 > /proc/sys/vm/drop_caches; free
              total       used       free     shared    buffers     cached
Mem:       2097152     334528    1762624          0        848      32364
-/+ buffers/cache:     301316    1795836
Swap:      8193064        652    8192412
==================================

Presumably I get more free memory but it gave no change for dd and/or tar.

My scanning the Internet on this issue gave just a little.

Does anybody know how to make commands 'dd' and 'tar' running again 
without reboot ?


Many thanks in advance for any ideas.


Andrey


-- 
____________________________________________________________________
NAME: Andrey Y. Shevel (Chevel) :  EMAIL: [log in to unmask]  \
Computing Systems Department    :     http://hepd.pnpi.spb.ru/CSD     |
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