[dm-devel] Multipath / iSCSI issues

[Mike Christie]

On 02/24/2013 01:15 PM, Devin wrote:
> 
> I am running Oracle Enterprise Linux 5.8 (which is really just Redhat).
> I am using Multipath and I have LUNS presented to me via iSCSI from a
> Hitachi SAN. I have the NICS bonded using the Linux bonding driver and
> using Active-Backup mode. I notice that when I loose a switch or
> connection to one of the switches that multipath freezes for at least 60
> seconds before it starts to respond again. Also it appears that IO being
> generated freezes until multipath responds again, this pause up to 60
> seconds is causing my Oracle instances to crash.
> 
> I have not been able to easily find what settings i could possibly
> change to make it fail to a new path faster. It almost seems like it's
> taking multipath a bit to fail all IO to a new path that is working.
> 
> Is there any information that might be useful for me that I can check on
> either the multipath side or the iSCSI side to see what is causing the
> issue???
> 

What iscsi driver are you using? If you are using software iscsi that
comes with OEL 5.8 what are our node.session.timeo.replacement_timeout,
.timeo.noop_out_timeout and .timeo.noop_out_interval. And what is your
scsi command timeout. You can see that by doing:

cat /sys/block/sdX/device/timeout