[ovirt-users] oVirt Instability with Dell Compellent via iSCSI/Multipath

[Nir Soffer]

----- Original Message -----
> From: "Chris Jones - BookIt.com Systems Administrator" <chris.jones at bookit.com>
> To: users at ovirt.org
> Sent: Friday, May 22, 2015 8:55:37 PM
> Subject: Re: [ovirt-users] oVirt Instability with Dell Compellent via	iSCSI/Multipath
> 
> 
> > Is there maybe some IO problem on the iSCSI target side?
> > IIUIC the problem is some timeout, which could indicate that the target
> > is overloaded.
> 
> Maybe. I need to check with Dell. I did manage to get it to be a little
> more stable with this config.
> 
> defaults {
>      polling_interval 10
>      path_selector "round-robin 0"
>      path_grouping_policy multibus
>      getuid_callout          "/usr/lib/udev/scsi_id --whitelisted
> --replace-whitespace --device=/dev/%n"
>      path_checker readsector0
>      rr_min_io_rq 100
>      max_fds 8192
>      rr_weight priorities
>      failback immediate
>      no_path_retry fail
>      user_friendly_names no

You should keep the default without change, and add specific settings under
the device section.

> }
> devices {
>    device {
>      vendor                   COMPELNT
>      product                  "Compellent Vol"
>      path_checker             tur
>      no_path_retry            fail

This is mostly likely missing some settings. You are *not* getting the settings
from the "defaults" section above.

For example, since you did not specify here "failback immediate", failback for
this device defaults to whatever default multipath chose, not the value set
in "defaults" above.

>    }
> }
> 
> I referenced it from
> http://en.community.dell.com/techcenter/enterprise-solutions/w/oracle_solutions/1315.how-to-configure-device-mapper-multipath.
> I modified it a bit since that is Red Hat 5 specific and there have been
> some changes.
> 
> It's not crashing anymore but I'm still seeing storage warnings in
> engine.log. I'm going to be enabling jumbo frames and talking with Dell
> to figure out if it's something on the Compellent side. I'll update here
> once I find something out.

Lets continue this on bugzilla.

See also this patch:
https://gerrit.ovirt.org/41244

Nir