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? Thanks, Tom _______________________________________________ rhelv5-list mailing list [email protected] https://www.redhat.com/mailman/listinfo/rhelv5-list
