What if I put more memory in a host than ESX can handle?

[Gabrie1]

Hi

Current host has 40Gb RAM, we might upgrade to more. When looking at pricing and free memory banks, we might go to 80Gb RAM, although ESX 3.0.x can only handle 64Gb. We plan to migrate to ESX 3.5 soon, so then the 80Gb can be addressed. Now I was wondering, would it hurt to put more memory in the host then it can handle?

Gabrie

[spuliven]

Just go through : http://communities.vmware.com/message/632903

[Gabrie1]

Hi

Can't find anything about putting more memory in the host than ESX can handle.

Gabrie

[jhanekom · Accepted solution]

ESX 3.0.x will in all likelyhood not boot up if you put more than 64GB of RAM in. The reason is that, on a system of that size, you will likely have at least two NUMA nodes and, since ESX only "sees" the first 64GB of RAM, it might not truncate the memory evenly from the multiple NUMA nodes. Couple this with the requirement that memory must be balanced equally amongst NUMA nodes, and you get a system that will probably not boot up.

Of course, if you have the budget now and might not have it later, nothing prevents you from buying the memory now and just leaving it in the cupboard somewhere...

KB1000087: On NUMA Systems With More Than 64GB RAM, ESX Server Host Might Fail to Boot

[TomHowarth]

good call, my view is that it will kernel panic, however I have no evidence either way it is just a gut feeling I don't have spare 64 GB of memory and a server powerful enough to take it

Anybody care to offer one? lol

Tom Howarth

VMware Communities User Moderator

[Gabrie1]

Thank you very much !!! Think I leave them out untill we upgrade to esx 3.5

My disabling NUMA could prevent the error, but this can impact performance. So I just leave them out

Gabrie