[Linux-cluster] General question about cluster

[Robert Peterson]

Fedele Stabile wrote:
> Dear readers,
> 
> i have this equipment:
> - 33 PC for student use
> -  2 servers and 1 SAN connected via SCSI to the servers
> only SAN and servers are powered by UPS
> 
> The whole equipment is in a private network, only servers are also 
> connected a public net.
> 
> I would export disks on SAN as a common filesystem for all computers.
> 
> I'm thinking it would be a good idea to use the cluster suite.
> 
> What is your opinion?
> 
> I installed CentOS+ClusterSuite and configured cluster to have 
> sufficient votes for servers (30 votes each)
> to avoid quorum problems in case of occasional student-PC switching-off.
> SAN disks were gfs filesystems and exported via GNBD
> 
> Cluster is working fine even if i power-off some of student-PC,
> but if i power-off all 33 student-PC the two servers go in hang,
> 
> remember that
> every student-PS has 1 vote
> every server has 30 votes
> (i can verify with cman_tool nodes)
> 
> so i have (as i can see with cman_tool status):
> 
> Nodes: 35
> Total_votes: 93
> Quorum: 47
> 
> also if all nodes are booting simultaneously they hang waiting 
> indefinitely for the clvmd start
> 
> Can you help me to find the mistake?
> 
> 
> Fedele STABILE
Hi Fedele,

We could probably give you more help if you told us your goal, what
you are trying to achieve with your configuration.  It would also be
nice to know what software you are running for Cluster Suite,
whether it's the "old" (RHEL4, STABLE) infrastructure or the "new"
(RHEL5, HEAD) infrastructure.

If your SAN is only connected to the two servers, then you only
need to cluster those two and use GFS to get the servers to cooperate 
with the file system on the SAN.  Then perhaps you can use something
like nfs to export the SAN data in GFS to the 33 student PCs.

If you're clustering all the student PCs for a specific purpose,
then perhaps you could share that.
Using the student PCs in the cluster may have some disadvantages
as you observed: At least 18 of the nodes (16 student PCs plus the
two servers) need to be up to maintain quorum.

Regards,

Bob Peterson
Red Hat Cluster Suite