Should all hosts in a cluster be the same spec

[wattieuk]

I am a relevant newbie to vmware and have recently installed a new 4 node cluster, all ibm x3850 m2's all identical specifications, I am now upgrading some old ESX 2.5 hosts to 3.5 and enabling for both HA and DRS. I'm running 3.5 update 1 and vc 2.5....

I have 2 x clusters one for the x3850's and one for the older x445's, but the x445's but they are all different spec.

1 x 16way 2.6ghz , 64gb,

1 x 16 way 2.6ghz, 32gb,

1 x 8 way 2.6ghz, 24gb,

1 x 8 way 1.5ghz , 16gb

Would i be better with 3 x clusters 1 for the 16ways, 1 for the 8ways and ensure the memory is distributed evenly, or can i keep untouched?

My head is telling me i'm wrong to have such varied capacity in a single cluster, I can't help but think I could get better utilisation of hardware if i re-worked the setup

[RParker]

Normally it doesn't make a difference however the CPU should be all the same family.

53xx 7xxx etc..

Update the 1 x 16way to 64Gb and those should be fine.

The other 2 there is too much difference in the CPU speed, you can still use them, just don't cluster them.

[mcamp001]

the short answer is yes, they should be the same. Will it work if they are not? Yes, but two major issues I have come across:

1) different CPU types - at a minimum you should always have the same CPU type across all cluster nodes, this will avoid some masking issues. These issues are well documented, just search

2) possible contension if resources are not equal across the hosts. This is especially prevalant when using multiple core VM's (2 or 4 cpu cores). Depending on how many vm's you have on each host (DRS will adjust this) you can run into performance issues if the VM has to be transferred to a 'lesser' host. There is a good thread on here regarding 4 CPU VM's, sorry no link, but search and read, good info.

hope this helps.