zoomin
Contributor
Contributor

esxtop and iops

Hello,

I'm trying to track down performance issues in our esx(i) 3.5 servers. I've been reading all the vmware docs, mostly working with esxtop.

My understanding is that cmd/s in resxtop are the same as iops.

On one new server, a sunfire x4150, with 8 SAS 10k 137GB disks in raid 10. This should provide a theoretical IOps (if one disk is 125) of 500. If I run IOmeter in a windows 2003 VM, I can easily push 1000+ IOps, as reported by IOmeter and resxtop. I've given IOmeter an 8GB file (VM has 4GB of RAM), so there shouldn't be a cache in the way.

Using the same methodology on my HP DL385s and the reports IOps seems to be inline with the theoretical.

I've tried other tools (in a linux guest, iozone and bonnie+) and resxtop reports very large cmd/s. With the right workload I can reach 3500.

I must be missing something. Any suggestions as to what I might be over looking?

Thank you.

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4 Replies
RParker
Immortal
Immortal

My understanding is that cmd/s in resxtop are the same as iops.

I don't think so, IOPS is the DISK performance, cmd/s is the number of COMMANDS sent to the disk. Not the same thing. A high amount of commands just means there is a lot of chattering to the DISK, doesn't mean those commands are doing anything useful.

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mittim12
Immortal
Immortal

Add the reads/s and writes/s to get your IOPS.

http://communities.vmware.com/docs/DOC-5240






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ablej
Hot Shot
Hot Shot

You can also get the IO information easily from the VI client under the performance tab. Sometimes it's easier to find and read what your looking for there.






David Strebel

www.cloudabstraction.com

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David Strebel www.david-strebel.com If you find this information useful, please award points for "correct" or "helpful"
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admin
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Immortal

>> My understanding is that cmd/s in resxtop are the same as iops.

Yes, it is. cmds/s ==> I/O commands issued per second.

>> On one new server, a sunfire x4150, with 8 SAS 10k 137GB disks in raid 10. This should provide a theoretical IOps (if one disk is 125) of 500.

Depends. If you are talking about 8K 100% random 100%writes, then Yes. For 8K 100% random 100%reads, you can expect 1000 IOps.

>> I've tried other tools (in a linux guest, iozone and bonnie+) and resxtop reports very large cmd/s. With the right workload I can reach 3500.

What is the I/O profile you used to push 3500+ IOps?

Chethan

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