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Old 10-12-2004, 09:06 AM   #1
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Registered: Oct 2004
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Distribution: Fedora Core 2 kernel 2.6.5-1.358
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Due to time out, SCSI bus reset and device offline


I am using a Linux server (Fedora Core 2) and am experiencing problems with a SCSI library.

Due to an unknown SCSI problem, a timeout occurs on the SCSI and the Linux server tries to fix the problem performing the following steps:
1. aborts the SCSI command that has timed out
2. attempts to reset a SCSI device
3. attempts to reset a SCSI bus reset
4. attempts to reset a SCSI host bus adapter

If all these fail, the device is then set "offline" which means that it is no longer accessible.

I tried the sg_reset command to bring the device accessible but it does work. The device remains offline.
The only working "reset" is to reboot the server.

Does someone know if there is a possibility to have the device back accessible (online) without having to reboot the server.

Old 10-12-2004, 11:04 AM   #2
Registered: Nov 2003
Location: austria
Distribution: debian
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what hardware (controller + drive) is this happening on?

sometimes drives need a long time to actually respond to a reset so maybe raising the bus reset delay can help.

if your kernel is compiled with scsi logging support you're able to raise logging verbosity by issuing a command to the driver - have a look into your driver dokumentation/source code about this.

sl mritch.
Old 10-13-2004, 04:10 AM   #3
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The hardware is a standard off-the-shelf Server with an Adaptec AHA-2944UW driving an IBM 3583 library.

The timeout error itself does not worry me too much.
What worries me is the fact that when a timeout occurs, the device goes offline and becomes unavailable. I haven’t found yet how to bring the device back online with a command/program.

Currently I must reboot the Server, which is not very funny when the problem happens over the weekend and my backups are not performed.

I designed a driver to drive the library and when a timeout error occurs, the library becomes unavailable. Any reset I tried does not re-enable the device.

After a timeout, here is what happens (the device is still there but it is unavailable):

# cat /proc/scsi/scsi
Attached devices:
Host: scsi0 Channel: 00 Id: 06 Lun: 00
Vendor: IBM Model: ULT3583-TL Rev: 2.80
Type: Medium Changer ANSI SCSI revision: 02

I have a little program that sends a TetUnitReady to the device:
testscsi <dev> <LUN> <command> where the command is a TestUnitReady

# ./testscsi /dev/sga 0 0

[E] Unable to open SCSI device /dev/sga, errno=6 (scsilib/SCSIOpenDevice).
[E] Unable to connect to device /dev/sga (testscsi/main).

I get back an error 6 which means the following:

#define ENXIO - 6 - No such device or address

According to some Linux doc I found on internet linux forums (, putting the device offline may be a normal behaviour, but it does not help me.

Anyway, if someone has a “workaround” to reset the device online without rebooting, this would be great.

Old 10-13-2004, 10:51 AM   #4
Registered: Nov 2003
Location: austria
Distribution: debian
Posts: 667

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has this just started or have you set up the system lately? is it random? does it continue spinning?
you can try the scsi-tools to down/up the disk, but as even a host reset doesn't get the drive back online i dont think it will be any help.

check/change cables helped me a few times now solving scsi-probs.
if modern drives get too hot they are able to offline themself.
anyway iirc errorcode 9 would be timeout - don't know about 6.
i'd suggest to enable verbose scsi logging and check if you can get more info on this issue.

sl mritch.


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