SCSI or libata problem with an RDX removable disk

[Pascal GREGIS <pgs@synerway.com>]

Hello everyone,

I turn to you with a new problem about scsi or libata.
I have a removable disk of type RDX, connected by SATA to my linux machine.
I access it via libata on /dev/sdb, like a classical disk.
I write to it a certain time with some mounts and umounts.
After a certain number of mounting and unmounting, or maybe a certain number of hours (not clearly identified), the device refuses to be mounted, saying "You must specify the filesystem type.".
Looking to /var/log/messages I have the following logs :


Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] READ CAPACITY failed
Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK,SUGGEST_OK
Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] Sense not available.
Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] Write Protect is off
Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] Mode Sense: 00 00 00 00
Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] Asking for cache data failed
Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] Assuming drive cache: write through
Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] READ CAPACITY failed
Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK,SUGGEST_OK
Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] Sense not available.
Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] Write Protect is off
Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] Mode Sense: 00 00 00 00
Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] Asking for cache data failed
Jul 15 14:55:54 testrdx kernel: sd 0:0:1:0: [sdb] Assuming drive cache: write through

These lines are logged again when I run cfdisk or parted or hdparm or anything
on /dev/sdb.

My system is :
linux kernel 2.6.21.1 with some patches :
- libata-start_stop_management (http://bugs.gentoo.org/attachment.cgi?id=118829)

compiled with libata.

Motherboard ICH6 family (id 2651)

Does anyone know this problem or have an idea about what it is and what to do?

Thank you in advance

Pascal