We use LUN masking in our setup so that even though e.g. we have 2 or more paths to the same SAN volume, fdisk -l will only show one disk per volume. Also, if you have e.g. 3 volumes assigned and have 3 FC paths, that could be the scenario where you will see 9 devices without LUN masking.
HTH. > --- On Thu, 1/22/09, [email protected] < > [email protected]> wrote: > > From: [email protected] <[email protected]> > Subject: Re: [rhelv5-list] Getting many paths attached to each lun > To: [email protected], "Red Hat Enterprise Linux 5 (Tikanga) > discussion mailing-list" <[email protected]> > Cc: "Red Hat Enterprise Linux 5 (Tikanga) discussion mailing-list" < > [email protected]>, [email protected] > Date: Thursday, January 22, 2009, 7:49 AM > > > In redhat5.2 , I have 3 luns (symmetrix) attached to the server. > > Just after installation when I checked > > > > with 'fdisk -l ' command , found each luns are attached to 9 > paths. > > I'd be curious how you have your san and lun configured, both hardware and > software. Atleast in a basic sense. I'll explain why in a moment. > > > I dont have any concepts still yet about multipath, though > > multipath rpm is being installed but the > > > > daemon is not started. > > I would recommend reading up on multipath, i've included some links below. > > > Later , I installed EMC powerpath and also found each lun is > > attached to 9 luns. > > In my experience, unless you have a good reason to use PowerPath over the > distribution tools, I wouldn't. Not to say that there aren't good > reasons. > This is a good read: > > http://blog.thilelli.net/post/2009/02/09/Comparison:-EMC-PowerPath-vs-GNU/Linux-dm-multipath > and has some links to some other good multipath and storage info > > > My qs is why i am seeing 9 paths attched to each lun? I need two > > paths attach to each lun. > > Like I said earlier, 9 paths is an interesting number. In every non-failed > scenario I've experienced its always been an even number, but this can > depend heavily on how your system is attached to the SAN. Effectively you > are supposed to get a device per path to that LUN. For example, if I have > a SAN with 4 paths to two switches and each switch has 2 paths to my > server. If I configure the switch to give each path on each side access to > the other (in other words SAN A0 would be one path to the switch, but then > could go over both paths from switch to the server), then I should end up > with 8 paths. > > > Any advice/suggession is really appreciated. > > As good of a starting place as I can find would be here: > > http://kbase.redhat.com/faq/docs/DOC-3691 > >
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