Quick report:

LTO2 drive, gentoo linux 2.6.27, amanda 2.6.1p1 OR 2.5.2p1 ...

This installation has run smooth for months without a change, now we get
hangs with amcheck .... amdumps also don't work.

I tried to downgrade to 2.5.2p1 to cross-check, but it also leads to dmesg:

st0: Block limits 1 - 16777215 bytes.
INFO: task amcheck:8309 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
amcheck       D 00000000ffffaadc     0  8309   8308
 ffff880119d17c88 0000000000000082 0000000000000000 ffffffff803ec550
 ffff88011d96f990 ffffffff806ef340 ffff88011d96fbc0 0000000000000000
 00000000000000ff ffffffff804a1c7f 0000000000000000 0000000000000000
Call Trace:
 [<ffffffff803ec550>] elv_next_request+0x183/0x193
 [<ffffffff804a1c7f>] scsi_request_fn+0x339/0x38f
 [<ffffffff805a8099>] schedule_timeout+0x1e/0xad
 [<ffffffff804a1104>] scsi_execute_async+0x328/0x375
 [<ffffffff805a785c>] wait_for_common+0xc8/0x132
 [<ffffffff80227f05>] default_wake_function+0x0/0xe
 [<ffffffff804bc3f9>] st_do_scsi+0x235/0x265
 [<ffffffff804bbbfa>] st_sleep_done+0x0/0x5f
 [<ffffffff804bcf48>] st_int_ioctl+0x608/0x984
 [<ffffffff804c05ab>] st_ioctl+0xaba/0xe44
 [<ffffffff802614a2>] handle_mm_fault+0x2a1/0x6be
 [<ffffffff80265194>] vma_merge+0x147/0x1f4
 [<ffffffff80283415>] vfs_ioctl+0x21/0x6b
 [<ffffffff8028369a>] do_vfs_ioctl+0x23b/0x24c
 [<ffffffff802836e7>] sys_ioctl+0x3c/0x5d
 [<ffffffff8020b1eb>] system_call_fastpath+0x16/0x1b


The drive is rather new, cleaned, the server rebooted, the cables
checked ...

We are now trying to find the source of the problem:

kernel, hardware, application?

Could someone help us to read those messages above?
Smells like hardware, hmm?

While I am typing this the admin there reboots the machine and tries to
access the drive via tar ... mt-commands work fine ...

Thanks, Stefan

(I'll be happy to give more info a bit later, in a hurry now)