On Thu, Jun 07, 2007 at 10:29:54AM -0400, Tom Sightler wrote: > Has anyone out there played around with the root on multipath support in > RHEL5? I just did an install on one of our IBM HS21 blades connect via > fiber channel to our EMC Claiion CX700 using the "linux mpath" install > method. The install went great and everything seemed completely fine. > There were a few things I had to clean up, like telling multipathd to > actually start by default, and removing the blacklist > from /etc/multipath.conf, but for the most part it was a breeze. > > However, in looking at the way RHEL5 creates the multipath devices > during the initrd process, it seems to me this might be a huge weakness. > The init file in out initrd image has the following section: > > echo Making device-mapper control node > mkdmnod > mkblkdevs > rmparts sde > rmparts sdc > rmparts sdg > rmparts sda > dm create mpath0 0 75497472 multipath 1 queue_if_no_path 1 emc 2 1 > round-robin 0 2 1 8:0 1000 8:96 1000 round-robin 0 2 1 8:32 1000 8:64 > 1000 > dm partadd mpath0 > rmparts sdh > rmparts sdb > rmparts sdf > rmparts sdd > dm create mpath1 0 10485760 multipath 1 queue_if_no_path 1 emc 2 1 > round-robin 0 2 1 8:48 1000 8:80 1000 round-robin 0 2 1 8:16 1000 8:112 > 1000 > > My reading of this means that the multpath devices are created during > boot time using static device names/numbers. The problem with this is > that, in most SAN environments, there is no way to guarantee that these > devices will always be discovered in the same order. Doing something as > simple as removing an adapter or adding a new LUN can drastically change > the device names and major/minor numbers (or perhaps even an actual SAN > path failure). > > This feels somewhere between extremely fragile and completely broken. > Am I misinterpreting this? >
Yes, it's broken. Just add another LUN to both HBAs and you lose the root device multipath.. It just doesn't get set up anymore. Hopefully this will be fixed soon.. -- Pasi _______________________________________________ rhelv5-list mailing list [email protected] https://www.redhat.com/mailman/listinfo/rhelv5-list
