Application Workloads and Performance

It's no secret, we love performance tuning at AnandTech IT. It is simply in our blood to want to get the very best out of each platform available to us, and especially on as sticky a subject as virtualization. During the past year of intensive virtualization research at our lab, and the building up of our own "real world" benchmark suite, we have encountered countless applications that take quite a bit of work to get performing as expected with virtualization.

We know that in the past, virtualization vendors' claims of virtualization providing virtually no overhead "out of the box" tended to be rather blatantly false. Their claims considered only CPU-intensive applications, requiring little of any other resource, ruling out I/O-intensive platforms like databases as ripe for virtualization. At this year's VMworld, VMware sought to see this perception changed, by organizing several sessions that focused solely on the performance of exactly these kinds of applications.

This series of two articles will be a culmination of those sessions, mixed with our own experiences with performance optimization. The aim is to help our readers with a virtualized data center to avoid the common pitfalls and feel confident in their ability to get the most out of the technology.

Naturally, we don't like just handing out this information without any context to our readers. As IT researchers ourselves, we are all too familiar with the "random web search approach", where you need to find a fix for something quick and end up trying out the first one the search results offer - sometimes with disastrous results. For that reason, we want to bring you answers and solutions, only with a dash of knowledge added in.

A Quick Overview of ESX
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  • najames - Tuesday, June 23, 2009 - link

    This is perfect timing for stuff going on at work. I'd like to see part 2 of this article.
  • - Wednesday, June 17, 2009 - link

    I am very curious how vmware effects timings during the logging of streaming data. Is there a chance that some light could be shed on this topic?

    I would like to use vmware to create a clean platform in which to collect data within. I am, however, very skeptical about how this is going to change the processing of the data (especially in regards to timings).

    Thanks for any help in advance.
  • KMaCjapan - Wednesday, June 17, 2009 - link

    Hello. First off I wanted to say I enjoyed this write up. For those out there looking for further information on this subject VMware recently released approximately 30 sessions from VMworld 2008 and VMworld Europe 2009 to the public free of charge, you just need to sign up for an account to access the information.

    The following website lists all of the available sessions

    and the next site is the direct link to VMworld 2008 ESX Server Best Practices and Performance. It is approximately a 1 hour session.">


  • yknott - Tuesday, June 16, 2009 - link

    Great writeup Liz. There's one more major setup issue that I've run into numerous times during my ESX installations.

    It has to do with IRQ sharing causing numerous interrupts on CPU0. Basically, ESX handles all interrupts (network, storage etc) on CPU0 instead of spreading them out to all CPUS. If there is IRQ sharing, this can peg CPU0 and cause major performance issues. I've seen 20% performance degradation due to this issue. For me, the way to solve this has been to disable the usb-uhci driver in the Console OS.

    You can find out more about this issue here:">


    This may not be an issue on "homebuilt" servers, but it's definitely cropped up for me on all HP servers and a number of IBM x series servers as well.
  • LizVD - Wednesday, June 17, 2009 - link

    Thanks for that tip, yknott, I'll look into including that in the article after researching it a bit more!
  • badnews - Tuesday, June 16, 2009 - link

    Nice article, but can we get some open-source love too? :-)

    For instance, I would love to see an article that compares the performance of say ESX vs open-source technologies like Xen, KVM! Also, how about para-virtualised guests. If you are targeting performance (as I think most AT readers are) I would be interested what sort of platforms are best placed to handle them.

    And how about some I/O comparisons? Alright the CPU makes a difference, but how about RAID-10 SATA/SAS vs RAID-1 SSD on multiple VMs?
  • LizVD - Wednesday, June 17, 2009 - link

    We are actually working on a completely Open-Source version of our vApus Mark bench, and to give it a proper testdrive, we're using it to compare OpenVZ and Xen performance, which my next article will be about (after part 2 of this one comes out).

    I realize we've been "neglecting" the open source side of the story a bit, so that is the first thing I am looking into now. Hopefully I can include KVM in that equation as well.

    Thanks alot for your feedback!
  • Gasaraki88 - Tuesday, June 16, 2009 - link

    Thanks for this article. As an ESX admin, this is very informative.
  • mlambert - Tuesday, June 16, 2009 - link

    We must note here that we've found a frame size of 4000 to be optimal for iSCSI, because this allows the blocks to be sent through without being spread of separate frames.

    Can you post testing & results for this? Also would be interesting to know if 9000 was optimal for NFS datastores (as NFS is where most smart shops are using anyways...).
  • Lord 666 - Tuesday, June 16, 2009 - link

    Excellent write up.

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