HOT off the presses !! EMC just released today a new whitepaper called “Sizing EMC VNX Series for VDI Workloads” <Click here to download if you don’t have a Powerlink Account> that goes into some GREAT detail on how to properly understand some of the metrics you need to pay attention to when designing Virtual Desktop Solutions, as well as how to apply that to the EMC VNX Product Family. If you are an EMC TC, Partner TC or Customer that is in the process of designing a VDI solution I would put this on the “Must Read” list. I thought I would call out a few of the things in the whitepaper you should pay attention to.
First and foremost understand that there is a sizing and architectural design difference between Citrix Provisioning Services (PVS) as Citrix Machine Creation Services (MCS) so when you are trying to decide on which Virtual Desktop solution to move forward with, it’s not as simple as Citrix VS VMware View. There are 2 different products for Citrix. Not to mention Citrix XenApp on top of that. I’m not saying one is better than the other, but just keep in mind that you need to pay attention to it from a design perspective.
Second thing to watch out for is understanding the different types of IO profiles. Page 15 of the whitepaper goes into some great details but allow me to point out that Virtual Desktops is a NASTY NASTY workload. Case in point, a typical enterprise application like Oracle, SQL, Exchange etc is usually described, from an IO profile perspective as 80% Reads and 20% Writes. It’s how we design solutions, size arrays etc. VDI is the exact opposite. It’s 70% to 80% Writes and the rest is Reads. So mixing of these two IO Profiles on a storage platform requires you to make sure you size them independently. I usually recommend dedicating an array (depends on the number of desktops) for VDI, especially if you plan on going beyond 500 desktops or so. Think of it as mixing Test/Dev applications with production. It sounds great in theory, until one day the developers decide to run some sort of IO thrashing process at it to find bugs in their code and it causes your production environment to crater. Trust me, it happens more times than you would think, and it doesn’t matter what storage solution you use ! Now imagine some issue that requires a bootstorm, login storm or Antivirus storm kicking off in the middle of the day. It has the potential to kill your production environment really quickly. If you are just playing around with VDI its perfectly fine to mix it with your production environment but just understand that you will want to watch this closely as you scale.
My first two thoughts above were purely vendor neutral but the following one is geared specifically to EMC VNX users. Page 22 is the start of the EMC Product focused content (took us 22 pages to get to the EMC stuff). First thing you start to realize is FAST Cache is AWESOME for VDI workloads (more info on this on page 26). On page 23 we specifically call out the three different VDI solutions (PVS/MCS/View) and apply all the math that we discussed in the Whitepaper on how to look at this from a building block perspective. For instance, we use 1000 desktops as a building block and describe the number of drives and SSD drives to support that workload. In this case, for 1000 VMware View desktops we would start with 2(ea) SSD drives for FAST Cache and 15(ea) 15k SAS drives in a RAID 5 configuration. If you need 2000 desktops, double it. If you need 3000, well I’m sure you get the point. Please note, these desktop sizing numbers are based on the math used in the whitepaper so if you choose to use different numbers, then your mileage will vary on the sizing but we teach you how to size so it shouldn’t take much to use your own numbers. By the way, the one question I get a TON is “What model of VNX supports X desktops”. I’m always hesitant to give a number out simply because it has everything to do with the IO profile of your desktop but because we are using the published numbers in this doc, it was easy to extrapolate that out to the different VNX model numbers. Check out page 25 for more details. Again, your mileage will vary based on your real world numbers.
By the way, if you are wanting to see the numbers we used, on page 28 – 36 goes into the gory details that only those of you that like numbers would love !!
I have to say, I’ve been with EMC for about 19 months and continue to be blown away by the amount of information and free resources that are available to our customers. While I certainly understand that others in the storage world will try to use this information against us, I welcome the opportunity to talk with customers about it and appreciate the work it takes to test and produce this valuable information for our customers and partners. Very cool.