Should the RAM for a replaced ESXi Host the same as remaining ones ?

[TonyJK]

Hi,

We are running a cluster of ESXi 5.1 hosts - 2 of them are Xeon E7440 @ 2.4GHz (64GB RAM) and 1 of them is Xeon X5460 @ 3.16GHz (32GB RAM).

Currently, the memory utilization of all three ESXi hosts are around 60%.

We are going to replace the Xeon X5460 Server with a new physical server.  We would like to seek your advice how much RAM should be ordered (My manager concerns the cost of the new server).

Thanks

[Alistar]

Hello,

since the cluster should have all its hosts identical CPU-wise (core count & frequency) and Memory-Wise (at least Size), you should order a host with 64 GB RAM.

[TonyJK]

Dear Alistar,

1) Does 60% RAM Utilization for ESXi Host is high ?

2) Would there be any problem if we add more RAM to the new server ?  This is because my supervisor will not consider replacing the remaining two servers in the future AND I would like to boost the RAM presented to the cluster.

3) If we need to get the server CPU - Same core and frequency, I think it will be a good idea to ask vendor to give us suggestion on which model they think fits our situation.

Thanks

[Alistar · Accepted solution]

Hi again Tony,

1. No, this is not high at all. You should start worrying about it after you reach ~85-90%.
2. From my short experience with memory-imbalanced clusters, adding more memory wouldn't hurt as the DRS handles the memory slots & "host goodness" in a good way, but I am not really sure about how that would turn out in the long run. If you decide to present more memory to your server it would be feasible to upgrade the other two hosts sooner than later
3. Yes, asking the vendor would be the right thing to do. Be aware however that you will need to set up an Enhanced vMotion to comply with your next "oldest" CPU then, because you will have something else than X5460. I guess you will have to "step it up" a generation or two, depending on what you are getting.