On Thursday 10 April 2008 10:59, Phillip Bennett wrote: > > What do you mean by 'fencing solution'? I'm looking to only store data > there that can be read/written to by multiple servers. Shouldn't the > filesystem (GFS) take care of this? The data doesn't have to be fenced, it > just has to be available. > Any cluster system needs to be able to determine where control resides if only a portion of the nodes are available - this is fencing. Have a read off the stuff at the Linux-HA project, and google for Stonith.
Definitely read the GFS docs - http://www.redhat.com/docs/manuals/csgfs/admin-guide/s1-ov-perform.html Because you are in the unusual situation of having a machine with guaranteed availability within the cluster network (although not behaving as an equivalent cluster node) you could easily script the 'manual' fencing solution for GFS - but RTFM first. Note that cluster filesystems are designed for low-level concurrency and may acheive this by trading off performance. A quick google suggests there are comparisons of NFS, ext3 and GFS available. > And when you say OLTP, I presume you mean Online Transaction Processing? > I'm just figuring out your terms and reading up first, so I might not be on > your wavelength here... It's just straight data files. No databases or > anything... Yes, OK - so RAID 5 makes sense for a small network then (assuming that latency is not an issue). > > I also understand what you are saying in your last paragraph. I'm not very > articulate, as you can see! I was meaning that you can't access a SCSI > drive/device independent of the machine that's hosting it. Yes you can - you just need to set the id of the other adaptor to something other than 0 - people have been doing shared disks this way for years. iSCSI will happily work with mutliple host accessing the same disk. In both cases, though, you still need a cluster-capable filesystem if the disks are trully shared (as opposed to merely occupying the same bus with a failover option - but we're back to fencing again here). > > I have thought about this and I see what you mean about pushing the RAID > over the network (I think). I was wondering if it would actually work! > After reading about DRDB though, this is exactly what I'm trying to > achieve. Would there be any significant gain in using something like DRBD > over a software RAID1 on the host? Apart from the fact, it is DESIGNED to > do what I want, of course. :) > I'd always seen DRBD as something more of a realtime backup solution - and I can't envisage how you would use it from multiple hosts without a clusterFS again. HTH C. _______________________________________________ Scottish mailing list [email protected] https://mailman.lug.org.uk/mailman/listinfo/scottish
