Re: Enabling failover (multipath) support in qla2300 driver

[Tom Sightler <ttsig tuxyturvy com>]

On Mon, 2005-03-07 at 16:36 -0500, Vincent Aniello wrote:
> How do I enable failover (multipath) support for the qla2300 driver in
> RedHat Enterprise 4.0?
> 
> In RedHat 3.0 I added "ql2xfailover=1" to /etc/modprobe.conf, but that
> doesn't seem to work in 4.0.

Vincent,

The Qlogic driver included in RHEL4 does not have failover support.  It
was removed in the official 2.6 version of the driver because it's not
considered the "One True Way" for multipathing under Linux.

Unfortunately, the "One True Way" of using disk mapper appears to so far
be mostly a dream in the heads of a few kernel developers.
Unfortunately for those of us who need working multipath today this
isn't a good thing.  It may technically be possible to get multipath to
work if your willing to jump through a few rings of fire, but it appears
to nearly impossible without using tools that aren't even shipped with
RHEL4.

The easiest/only real solution I've found is to install the Qlogic
driver from the Qlogic website.  At this time the best option that I
have found is to download the beta version of the Qlogic driver from the
Qlogic FTP site ( ftp://ftp.qlogic.com/outgoing/linux/beta/8.x ).  This
version includes the same basic failover support at the 7.x series
included in RHEL3.

You can technically get this working with the SLES9 version from the
website, but a small bug keeps the failover support from compiling with
RHEL4.  The beta version solves this problem.

I realize it's still beta but I have been running the version on our
primary backup server for a couple of weeks now without even the
slightest problem.  This system mounts about 15 EMC snapshot volumes and
connects to a large tape library and a 2TB virtual tape array and hasn't
had a single hiccup.

I'm sure the disk mapper option will eventually be the absolute best
way, but I'd agree with others assessments that this may still be
several updates away from being ready for prime time.  If others have
discovered other options I'd sure love to hear about them.

Later,
Tom