TheVMinator
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vROPs Disk vs. Virtual Disk vs. Datastore Metrics

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What is the difference between these three types of metrics for a virtual machine?

1. Disk

2.  Virtual Disk

3.  Datastore

http://pubs.vmware.com/vrealizeoperationsmanager-64/topic/com.vmware.ICbase/PDF/vrealize-operations-...

I want to see the average total latency for a single virtual machine including all of its virtual disks, should I use the "datastore" metric or should I use the "disk" or "virtual disk" metrics and sum them? 

If I use "datastore" will that include informaiton from other virtual machines that have disks on the same datastore?

thanks!

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carvaled
Enthusiast
Enthusiast

So a quick one.. if you want more  detail let me know

The way I typically troubleshoot latency issues is by starting with the VirtualDisk metrics... this gives me a good indication of what the VM is experiencing... once I have looked at the aggregate and determined the VM is suffering I will then break it down to the individual SCSI id's of the disks and determine if it's a problem for only a specific disk on a dedicated datastore etc...

Using datastore latency is not always a good indication as you can have some faulty hosts but because the datastore metric is an aggregate of all ESX hosts latency to the datastore it can actually mask a real performance issues....

For example if you have 10 hosts connected to a datastore and 9 have low latency but 1 has high latency the latency is averaged out for that datastore to look like the performance is fine when in reality 1 host is suffering along with its VM's...

When I find high latency on a VM and then look at the datastore latency and it's low I suspect a problem with the paths to the storage for that host...so I will then look at the HBA latency for the host to break it down to a path.

Hope that helps.

Cheers

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carvaled
Enthusiast
Enthusiast

So a quick one.. if you want more  detail let me know

The way I typically troubleshoot latency issues is by starting with the VirtualDisk metrics... this gives me a good indication of what the VM is experiencing... once I have looked at the aggregate and determined the VM is suffering I will then break it down to the individual SCSI id's of the disks and determine if it's a problem for only a specific disk on a dedicated datastore etc...

Using datastore latency is not always a good indication as you can have some faulty hosts but because the datastore metric is an aggregate of all ESX hosts latency to the datastore it can actually mask a real performance issues....

For example if you have 10 hosts connected to a datastore and 9 have low latency but 1 has high latency the latency is averaged out for that datastore to look like the performance is fine when in reality 1 host is suffering along with its VM's...

When I find high latency on a VM and then look at the datastore latency and it's low I suspect a problem with the paths to the storage for that host...so I will then look at the HBA latency for the host to break it down to a path.

Hope that helps.

Cheers

View solution in original post

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sxnxr
Commander
Commander

If you have not already upgrade to 6.4 as there are some new dashboards that are good and may give you what you need

TheVMinator
Expert
Expert

OK great - thanks again!

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