[Linux-cluster] Advice on suitability

Ashley Large ashley at host365.com
Fri Nov 19 11:24:26 UTC 2010



I have been finding a fair bit of configuration info iro clustering, cluster
suite and gfs/2 but not quite seeing the more conceptual stuff with pretty
diagrams that would help me grasp whether its applicable to my needs so I
hope you can help with unscrambling my confusion. 


Currently I have 25 odd servers each running LAMP and qmail etc. Throughput
on each ranges from 1 - 10 mbits/s. Each currently works off raid 1 mirrored
disks and all are relatively low powered machines. Total storage usage for
all 25 machines is about 4Tb. I want to virtualize the whole lot (I am
leaning towards KVM). My motivations are 1) reduce power usage in rack and
2) build in as much redundancy as I can.


My thoughts have been to have 3 "front end" physical host machines with a
rough 50/50 split of the current 25 odd servers into VMs on these physical
hosts. I will then have redundancy across 3 machines so that if machine 1
dies, the vms are moved to machine 2 or 3 pending fix of machine 1. Then I
want to create two "back end" storage servers which are replicated and
provide redundant storage to the front ends in a primary/secondary way such
that the front ends can failover to either available storage server. I am
anticipating having only VM host booting off machine1-3 and using the back
end storage servers for booting the vms and storing their data. Each storage
server will have 6 x 2Tb sata disks set up as a 6Tb raid1 array although I
have been reading that more spindles is better so maybe I need more disks
for optimal performance. Front ends and back ends would have multiple bonded
Gig e ports to a dedicated switch which I think should provide enough
bandwidth and the net facing NICs running off a separate switch.


I have looked at openfiler and open-e for storage platforms which are
options but then followed some RHEL links to Cluster Suite, GFS2 and the HA
add ons and it began to look like another option for presenting a redundant,
automated-failover storage platform to the VMs using commodity hardware
rather than proprietary SAN kit.


So I am trying to work out if I am on the right track with Cluster
Suite/GFS/ etc and if so, what are the elements I need to meet my objective
and will it actually work and provide the throughput I need or are 25
web/mail servers doing constant reads/writes going to mean its all too slow.
I also saw some warnings about mysql usage on the cluster which looked
troubling. Any real world experiences, pointers or advice would be great.


Thanks and regards


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