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February 25, 2010


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Tweaking and upgrading our Clariion array got our clone times from 40 minutes down to 2 minutes. Our engineers almost bought me a cake.

Primary tweaks: Using a stripled metalun to get give our datastores more spindles (that got us to 20 minutes), and upgrading our SP to enable write caching (that brought it to 2 ;)

Matt Meyer

I have been battling this very issue since upgrading to ESX 4.0. My SAN is not exactly on the HCL, but with ESX 3.5, I was able to push cloning operations to 120 MB/s. With ESX 4.0, they run at about 5 MB/s. This sheds a lot of light on why that happens, so a big thank you for that. Now, can you think of any way to tweak the Data Mover in ESX 4.0?

Ron Singler

So I was just at this customer the past two days installing their new Hitachi USP-V. We were walking through things doing some KT and they mentioned that their new litmus test for performance of their storage systems was a VMware clone operation due to performance issues they found on their V-Max boxes. They stated that their Clariion boxes were way faster than the V-Max at this operation and we put a little wager on whether the USP-V would be faster than the Clariion.

I took that bet and ended up winning. ;) The clone operation finishes in a consistent 10 minutes or less. The resulting time is what the customer called "untuned". We didn't mess with the VMware I/O size and left everything at the defaults. I'm sure we could improve things if we tuned things to the 512KB stripe boundary on the USP-V.

I just thought it was funny that you posted this today because I was getting ready to write something up the next couple days on it. Thanks for saving me the time! Great article!


No matter how you try to spin it, EMC V-MAX should be smart enough to recognize a sequential stream and optimize for it, it's not exactly new technology :).

And you even call it V-MAX, the best virtualization storage...

I wonder how it performs with a MS SQL server doing full table scan due to a select query for a big report...


Great thread. I think I have this problem with vSphere and a CX3-10c. My vRanger performance when doing iSCSI backup from CX3 is terrible. Half as good as doing non-iSCSI backup.

Conversely I have an Equallogic PS6000XV and MD3000i all in the same fabric and they don't have performance issues. In fact non-iSCSI backup are half as fast as iSCSI.

any ideas?

Andrew Fidel

I actually have the opposite problem on midrange virtualized array, vsphere is able to push enough IOPS during a clone that it can actually push up response time on the volume, can't wait for I/O DRS =)


Has anyone been able to identify the reason for this behavior?

John Martin

Interesting post, overall I'd agree with your categorisation of Mid-Range vs Enterprise, though in the past I'd always thought that DMX was better suited to sequential workloads and single threaded large I/Os due to its mainframe heritage with the associated tendency to do batch processing, and that mid-range boxes typically had the advantage when it came to cache-hostile random I/O.

I based that assumption on a casual conversation almost a decade ago, where someone said that Exchange 2000 workloads were fairly toxic to early DMX implementations. I brought up that conversation with an EMC engineer who said that a revision of Enginuity addressed this. Even though this was based mostly on hearsay, it appears maybe this cloning situation is another example of a mismatch between the design center for the array and the particular workload.

I wonder if this had test had been done on an old-school hand tuned DMX whether the result would have been the same as I suspect that the design center for the Vmax workload is more highly optimised for small block random I/O than the previous Sym.

For single threaded workloads little law determines overall throughput, and the additional overheads associated with a scale-out architecture (even when measured in microseconds) can really drop sequential throughput, but I'm surprised that the impact is as large as it was.

As a matter of interest, did the customer try using PowerPath ? Your mention that using round robin would have improved things dramatically inferrs that they didnt, but if they'd gone to the expense of installing a V-Max why not complete the picture ?

Chad Sakac

John - thanks for the comment. The customer was using VI3.5, so use of Round Robin or PP/VE was out of the question, unfortunately. In the testing completed, we did show that going to vSphere 4 and using Round Robin or PP/VE did ultimately drive much higher bandwidth.


Great thread. I think I have this problem with vSphere and a CX3-10c. My vRanger performance when doing iSCSI backup from CX3 is terrible. Half as good as doing non-iSCSI backup. http://www.hotfilemediafire.com

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