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Re: [dm-devel] Multipath / iSCSI issues




I am using the iscsi tools that is included with Oracle (iscsi-initiator-utils-6.2.0.872-13.0.1.el5). 

The values I have in my iscsid.conf are:
node.session.timeo.replacement_timeout = 15
node.conn[0].timeo.noop_out_timeout = 1
node.conn[0].timeo.noop_out_interval = 1

{i have previously changed the settings from the values based upon some feedback I got from a tech guy but that didn't seem to make much difference}.

In regards to the scsi command timeout it appears to be set to 60.

# cat /sys/block/sdw/device/timeout 
60

So is my thinking correct that I will want to have the SCSI devices to timeout more quickly like 1 second versus the 60 seconds? If so where would i make this change in regards to the disks???

Thanks much.

Devin Acosta


On Sun, Feb 24, 2013 at 4:50 PM, Mike Christie <michaelc cs wisc edu> wrote:
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




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