[Lustre-discuss] multipathd or sun rdac driver?

[David Noriega]

They are 2540 and I'm running EL5(centos).

Well the thought came around since I had to rebuild a node after a
hardware problem. So I went ahead and gave it a shot. I think I posted
about this problem before somewhere in the mailing list about getting
stray I/O errors which were for /dev/sdX devices that were the other
path to the same device(Well thats the idea we came to). Well after
installing the Sun RDAC module and disabling multipathd, I can happily
say those messages are gone, so I suppose Sun's module is able to talk
to the disk array in a better manner then multipathd. Though I haven't
failed back the lustre ost's to this particular node just yet(will
wait till the weekend). I'll post again if anything goes wrong, but I
think going with this RDAC module might be better.

ps: One thing that has nagged me since Lustre was installed and setup
by a vendor, was the disk arrays were never setup with initiators or
hosts in the configuration(Using CAM). We have another similar disk
array(6140) we setup for another filesystem and I know
initiators/hosts were setup on the array. I can't say that this has
caused any problems, but its something in the back of my mind.

Thanks,
David

On Wed, Jul 20, 2011 at 4:15 PM, Kevin Van Maren
<kevin.van.maren at oracle.com> wrote:
> David Noriega wrote:
>>
>> We already use multipathd in our install already, but this was
>> something I wondered about. We use Sun disk arrays and they mention
>> the use of their RDAC driver to multipathing on Linux. Since its from
>> the vendor, one would think it be better. What does the collective
>> think?
>>
>> Sun StorageTek RDAC Multipath Failover Driver for Linux
>> http://download.oracle.com/docs/cd/E19373-01/820-4738-13/chapsing.html
>>
>> David
>>
>
> I assume you are using the ST25xx or ST6xxx storage with Lustre?  Exactly
> which arrays?
>
> I've been happy with RDAC, but I don't think Oracle has released RHEL6
> support yet
> (but Oracle also does not support Lustre servers on RHEL6 yet).
>
> If your multupath config is working (ie, you've tested it by
> unplugging/replugging cables
> under load and were happy with the behavior), I'm not going to tell you to
> change.
>
> Kevin
>
>



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