ONTAP Discussions

OnTAP Select Possible Memory Issue

TMADOCTHOMAS

Background: We recently deployed two Dell servers to serve as ESX hosts for a small office in our company. Each host has 96GB of memory, 16GB of which was reserved for an OnTAP Select node (it's a 2 node HA Pair, small size).

 

Despite the fact that they have 28 VMs, they use a very minimal amount of memory collectively. The Dell IDRAC memory stats show roughly 10 - 20% of memory utilization consistently. Having said that, the Host summary tab in vCenter constantly throws up "Host Memory Usage" alerts and shows that the hosts are nearly out of memory, even though iDRAC shows very little memory in use. This office wants to add a few more VMs but I was concerned about the memory allocation. After consulting with a VMware expert, we were told my analysis was correct and that since Dell showed little memory actually in use, we should be able to overcommit and add the additional VMs.

 

Four VMs were added and powered on. We experienced an outage in which the hosts froze up and VMs were inaccessible until we powered the new VMs off. During a second attempt in which they were powered on one at a time, a less drastic but similar problem occurred after powering on the second VM. 

 

We have cases open with NetApp and VMware but are having trouble making headway so far. Does anyone have insight into this issue? I can't understand why we would need more physical memory, yet the symptoms seem to indicate we do. The only VMs with reservations are the OnTAP Select nodes.

1 ACCEPTED SOLUTION

NetApp_SR

Looking in one of the Dell manuals  for iDRAC the "Memory Utilization" is not a measure of the memory that is in use. To quote it "This is a measure of memory bandwidth consumption and not amount of memory utilization."  I suggest ignoring the iDRAC and concentrating on managing the memory from vCenter. What does vCenter show for memory utilization for the host?

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4 REPLIES 4

NetApp_SR

Looking in one of the Dell manuals  for iDRAC the "Memory Utilization" is not a measure of the memory that is in use. To quote it "This is a measure of memory bandwidth consumption and not amount of memory utilization."  I suggest ignoring the iDRAC and concentrating on managing the memory from vCenter. What does vCenter show for memory utilization for the host?

View solution in original post

NetApp_SR

The link below is a white paper for ESX memory.

 

Understanding Memory Resource Management in VMware® ESX™ Server

https://www.vmware.com/content/dam/digitalmarketing/vmware/en/pdf/techpaper/perf-vsphere-memory_management.pdf

 

TMADOCTHOMAS

@NetApp_SR thank you. I had noticed that line in Dell's documentation just yesterday as I was looking into this further, and wondered if I was misinterpreting those statistics. If so, that is the root of our issue because vCenter shows high memory utilization from within vCenter. I'm starting to think that is 100% accurate, and as you are saying the Dell information may not report what it appears to. I think I will open a case with Dell and just get clarity on this subject.

 

Thank you very much for the link, I will review it.

TMADOCTHOMAS

@NetApp_SR , the phrase you pointed out was our root problem - a fundamental misunderstanding of the stats being presented in Dell's iDRAC. I opened a case with Dell this morning and they clarified that the stats show traffic between CPU and memory, not memory utilization. So, we simply have a memory allocation issue we need to resolve. Thank you for the help!

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