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md multipathing failover



Hi,

I am becoming a little desperate with my SAN (EMC Clariion, Qlogic HBAs)
connections.

With RHEL3 I just use the internal failover of the Qlogic driver. This
works fine. 

However, the Qlogic-modules in FC2, FC3 and RHEL4 lack this feature. I
therefore rebuild the kernel with the Qlogic-driver on some FC2/3 hosts
to have the same functionality as in RHEL3.

These FC2/3 hosts should be upgraded to RHEL4 quite soon. As the
failover is 
missing I tried to convert the SAN-attached filesystems to md
multipathing. 

In general it works fine, but I tested the failover on a FC2 host
(latest errata kernel). The result is that the md0_multipath thread
takes up all the CPU ressources but does not actually switch to the
alternate path.

Besides, the multipath device is not assembled in a correct way during
bootup on FC2 as it uses raidtools instead of mdadm, but I corrected
this at runtime, so this cannot be the reason.

Question: - Does multipathing actually work with RHEL4? Did anyone pull
the plug to test it? Does it work on RHEL3? Does it even work on FC2 and
I am just missing something?

Sorry for crossposting and referring to Fedora Core, but I hope some
RHEL admins also run Fedora. The guys on the Fedora lists do not seem to
deal with stuff like SANs.

regards, Gunther

-- 
Gunther Schlegel                    Riege Software International GmbH
Manager IT Infrastructure                                Mollsfeld 10
                                             40670 Meerbusch, Germany
Email: schlegel riege com                     Phone: +49-2159-9148-0
                                              Fax:   +49-2159-9148-11
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