GPFS Tiebreakers question

[MoreFeo]

Hi,

We've been asked to install and configure GPFS on 2 AIX servers (LPARs with AIX 5.3).
The idea is to map the same lun to both servers and use GPFS.

Now, someone has told us we need 3 more LUNs, to configure quorum with tiebreakers, but we don't know if it's mandatory.

Can't we configure the two servers without quorum and without these 3 tiebreakers?

Thanks

 

[p5wizard]

The quorum is mandatory. You need a lun with the GPFS metadata on each of the nodes (GPFS replicates all the data updates and metadata updates to the LUNs it maintains). When one node goes down, GPFS checks if a quorum (more than half) of the nodes in the cluster is still maintained in order to decide to keep the cluster up or bring it down completely. Without a third node, any node down results in the GPFS cluster down.

(this is from memory, so I'm not 100% sure about terms I used, but I am 100% sure about quorum rule)

Also IMHO it is better to have two copies of the data on two LUNs in two different computer rooms. Just present these two LUNs to the two data nodes and make them copies of each other in GPFS. You don't need 3 additional LUNs, just one additional LUN on the tiebreaker node will do. Can even be a logical volume in that tiebreaker node's rootvg. Just make sure the original LUN(s) are for data and metadata, the tiebreaker LUN is only for metadata.



HTH,

p5wizard