Hotplug SCSI disks + FC3 (2nd try)

T. Horsnell tsh at mrc-lmb.cam.ac.uk
Wed Apr 13 10:31:05 UTC 2005


>On Tuesday 12 April 2005 11:21 am, T. Horsnell wrote:
>> I'm still flailing around trying to understand why hotplugging
>> my SCSI disks doesnt work. 2.6.10 kernel, and the disks are seen
>> OK after a system boot. However any disks which are plugged
>> in with the system running, dont seem to generate any hotplug
>> activity (checked by modifying /bin/hotplug script to write to
>> a file when it runs).
>>
>> Should hotplugging SCSI disks work with 2.6.10 kernel?
>> If not, can anyone suggest how I might make the system see
>> the new disks without rebooting? I've tried kudzu with no
>> success (should *that* have worked?)
>
>No.  Unless you use special hardware (hot plug chassis with enclosure 
>management), the generic SCSI bus does not detect "plugs".  In addition, hot 
>plugging can be dangerous.  If there is data I/O going on on the SCSI bus at 
>the time you plug, you risk causing data corruption.  USUALLY this will be 
>detected as a bus parity error, or other failures which get retried.  But if 
>it doesn't...
>
>> Is there some other way to force a SCSI-bus scan?
>> (I see ../drivers/scsi/scsi_scan.c in the kernel source)
>
>If you look at the SCSI how to (www.tldp.org), it makes reference to a 
>command, something like "echo 'magic incantation' > /proc/scsi/...".  This 
>causes the specified device to be added to the internal tables. I don't 
>recall a rescan command, but I haven't looked in a while. If there is, it 
>would most likely be a similar echo command.  It should be in the same SCSI 
>how to.
>

Thanks for this Rick. I'm making a start on moving about 100 SCSI
disks from my Alpha system onto a dual Opteron one. Ive been hot-swapping
SCSI on the Alpha for many years,  so I guess I've been spoiled.
I didnt properly research hotplug SCSI on Linux before I started :(

Cheers,
Terry.




>> Thanks,
>> Terry.
>
>Your welcome,
>	--rick
>
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