On Wed, 2009-06-24 at 07:22 -0700, nate wrote:
Kris Buytaert wrote:
We're trying to setup a dual-primary DRBD environment, with a shared disk with either OCFS2 or GFS. The environment is a Centos 5.3 with DRBD82 (but also tried with DRBD83 from testing) .
Both OCFS2 and GFS are meant to be used on SANs with shared storage(same LUNs being accessed by multiple servers), I just re-confirmed that DRBD is not a shared storage mechanism but just a simple block mirroring technology between a couple of nodes(as I originally thought).
Actually, it's both. http://www.drbd.org/users-guide-emb/ch-fundamentals.html gives the overview. It's shared storage with local disk access. And if you're using Gig-E for the interconnect, it's *fast*. ;)
I think you are mixing incompatible technologies. Even if you can get it working, just seems like a really bad idea.
That functionality is built in. DRBD fully supports use of OCFS2 on top of it in dual-primary mode. See http://www.drbd.org/users-guide-emb/ch-ocfs2.html
Perhaps what you could do is setup an iSCSI initiator on your DRBD cluster, export a LUN to another cluster running OCFS2 or GFS(last I checked GFS required at least 3 nodes less than that and the cluster goes to read-only mode, I didn't see any minimum requirements for OCFS2).
You could do that, but it would probably be overkill. Too many moving parts. You'd also slow down the speed. You're talking about app node -> Gig-E -> OCFS2/GFS cluster -> Gig-E -> iSCSI/DRBD cluster. I'd rather have app node -> Gig-E -> OCFS2/DRBD cluster. And it's *much* easier to setup. GFS is a bit of a pita to setup. I used to do it for RH professionally and it's not entirely painless...
Though the whole concept of DRBD just screams to me crap performance compared to a real shared storage system, wouldn't touch it with a 50 foot pole myself.
Nah... performance is pretty sweet. Local disk access, sub-second resync after rebooting one of the nodes, and the cost is *much* lower than a "real" shared-storage system... if cost is a factor, I'd seriously consider trialing the DRBD/OCFS2 combo.