The VDI Read/Write Ratio Challenge

I spend a lot of time writing blog posts but I also spend time with customers and their VDI projects. During my time with customers I have identified that read/write ratios in VDI environments could be anything from 50/50 to 20/80 in favor of writes.

It turns out that every once in a while someone comes to me saying that a given VDI deployment have more read IOs than write IOs. Even if Windows guest image is optimized to extremes and applications virtualization is utilized I would still say VDI has more writes than reads. Well, am I wrong?


Why is that important?

This is extremely important when sizing the storage array that is going to support the VDI environment. Read my article Get hold of VDI IOPs, Read/Write Ratios and Storage Tiering to understand how the RAID type will determine the numbers of spindles required to support the workload based on the amount of IOPS and Read/Write ratio.


The Challenge

I would like to validate numbers with REAL Production data from various VDI deployments. With the results in hands I will publish an article that will help everybody to understand this skew a little better.

So, fill the form bellow with data from your organization. The data need to be REAL and the name of the company and email address is required for validation purposes. I will keep the data provided in absolute confidentiality.

The instructions about how to collect the data are bellow.

When the 100th survey is answered I’ll give away a USD $50 Giftcard (any country) for a lucky winner.


[form form-2]




  • Select the following day of a normal operations day for your VDI environment (for most organizations Tuesday trough Thursday)
  • Select a host in use by your VDI environment and go to the Advanced Performance Chart.
  • Select Datastore > Custom…, then select your organizations peak production time (for most organizations 8:00AM trough 5:00PM), then in Objects select active datastores supporting VDI VMs.
  • On Counters, select Average read requests per second and Average write requests per second.
  • Note: Take a screenshot of the configuration and the performance chart for validation, if required.



Below are the Maximum and Average numbers we want to consolidate.



Thanks for supporting this research!


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    • Ian on 10/04/2011 at 7:46 am

    Every cluster of VDI Hosts I have has different datastores available to it and as such have wildly different metrics across them for maximum and averages. How do you want to capture metrics like that? Also my clusters are a mix/mishmosh of Win7 32bit along with XP 32bit and are not separated out by any logical means. How does that change your numbers/discussion?

    • Smitty on 10/13/2011 at 1:34 pm

    Our implementation initially has 300ish VDI sessions with tiered storage with EFD hosting the replicas and 3 LUNS with 15k SAS drives. I’m assuming you’d like to have all datastores or perhaps exclude the EFD store as it will have 100% reads. Thx.

  1. @Smitty
    After boot and login I wouldn’t expect much activity on your Replica Lun. If you enter the numbers during your production hours the Replica should have minimal use. Verify the numbers and let me know here at comments.

  2. Good discussion as the common theme is VDI and reads along with bootstorms. However even on boot, there are some writes, not to mention writes if you are actually modifying or creating data as part of doing useful work. Then there is the corresponding discussion that rarely occurs which is opposite of boot and boot storms which is shutdown/hibernate storms, virus scan/maintence function storms and so forth.

    Fwiw/fyi, here is a post I did a few months back about windows read/write performance as part of VDI planning along with some metrics that I posted based on some quick tests using HyperIO HiMon tools for collecting stats.

    Measuring Windows performance impact for VDI planning

    Windows boot IO and storage performance impact on VDI


  3. I suppose it is of no use to enter your data twice? Can you confirm if our data was entered correct?

  4. @Pieterjan Heyse
    Your data is valid and you don’t need to re-enter. As always, thank you for your support!


  1. […] Want an opportunity to win a $50 gift card? Go supply your VDI read/write IOPS data statistics over at Andre’s site. […]

  2. […] the past few weeks I have been collecting data from my VDI Read/Write Ratio Challenge. Please, take a minute to help us understand the overall IO pattern of VDI deployments. […]

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