Posted by: tonywilburn | January 13, 2010

My first post – VDI storage

It’s a new year and I’ve decided to finally start the blog I’ve been threatening to write for over a year.  Some of the things that I write here will be helpful hints that stumble upon along the way.  Some, like this, will be in response to things that I have heard or read.  In this case, this post on got me to thinking.  Quite a few people are asking about using local storage for VDI implementations.  Personally, I disagree with using local storage for VDI.  Maybe, in a few instances it could be justified, but to me, the risks aren’t worth the rewards.

Somewhere along the way, the VDI message has been misconstrued.  I’ve heard cost as the deciding factor of whether VDI is implemented or not.  Just that, cost, and nothing else.  Maybe we are to blame, in today’s economy (don’t you hate that phrase), cost is the driving factor and vendors have used cost to try to sell VDI.  The problem is, at first blush, VDI isn’t cheaper than traditional PCs.  You have to figure in the cost of the VMware View license (I’ll look at this from a VMware perspective, but the same would apply to other solutions), the cost of the Microsoft license, XP, or Windows 7, assuming you aren’t using a Linux distro for your desktop.  Just these two licenses alone can be expensive, then add in the cost of the thin terminal, the host servers, and the shared storage and the price starts to mount quickly.  Pretty soon the cost is about the same as a traditional desktop.   Because of this, people have started looking for a way to cut costs.  Some just dismiss VDI and say that VMware must cut the cost of View.   Others look at the other pieces of the puzzle and in many cases, storage is the target.

I believe that shared storage is practical for two reasons.  First, competition is making storage cheaper and more efficient all the time.  Second, thanks to linked clones, the amount of storage needed is no longer astronomical.  With linked clones a hundred desktops can take up a few gigabytes versus the terrabyte that it would have previously taken.

Not only do I believe that shared storage for VDI is practical, it’s critical.  The most important element in the success of a VDI implementation is user experience.  No matter how great the design looks on paper, or what price you were able to negotiate, the bottom line is “Is the user happy?”  Today’s user is accustomed to having their desktop respond as soon as they move their mouse.  With shared storage and HA, you can guarantee that will happen.  Your users will never know that you have a server offline and are frantically working to bring it back online.  All they know is that they can continue to do their job.  This is what will make or break your VDI implementation.  This makes shared storage worth the cost.  With all the tools available with products like View, you can spin off a new image for your users in minutes, if you have another host lying around with enough local storage to handle the images.  But unlike the days of traditional PCs when you got one user call for broken hardware, you now have sixty or more.  That’s 60 phone calls that someone has to answer, 60 tickets that some helpdesk person will probably generate, and 60 irate users.  Even if it is for only an hour, that’s 60 users that are upset and that’s not a good situation to be in.

A last word on cost.  Sure VDI can seem costly, it’s a large upfront cost, and I only recommend doing a wholesale conversion to VDI when you need to upgrade your hardware and are already planning on a big expense.  So where are the cost savings?  Why move to VDI?  The cost savings come in a couple of areas.  One is the longevity of the systems.  A thin terminal is going to have a much longer life span than a traditional PC.  You also have the ability to do things like memory upgrades by allocating more memory to the VMs without having to buy more physical memory.  This will extend the life of the virtual desktops.  Another savings point that IT has to be mindful to champion is the savings in power and cooling.  Since PCs reside in the offices and not in IT, these savings will be seen by facilities and not impact the IT budget, so be sure to let management know where those facility savings are coming from.  The savings that impresses me the most though is manageability.  Simply put it takes less people, less time to manage a VDI infrastructure than it does a traditional PC infrastructure.  I’m not advocating people losing their jobs, but it does allow people to be used on projects and proactive activities rather than continually fighting fires.  According to research, all of these savings add up to a 12 to 18 month return on investment.  So, would I implement VDI if I were doing a massive upgrade project?  Yes.  Would I implement VDI in small phases where there were use cases to support it?  Yes.  Would I replace outdated hardware with thin terminals as they break or come up for retirement?  Yes.  Would I implement VDI with shared storage?  YES!



  1. Excellent first blog!

    I think it is important to consider SLA’s when thinking about desktop virt. Users on regular desktops/laptops have outages that last one to two days. We spend a lot of money getting SAN’s and infrastructure in our server virt world to get to 99.999% – do we need to match that in virtual desktops?

    There should be a place for local storage. With SSD fixing the I/O performance challenge, and new software solutions making local storage effective and reliable (disclaimer: I am the CTO of Unidesk, provider of one of those solutions), it seems that much of the storage cost challenge can be addressed without disrupting the SLA expectations of many use cases within organizations.

    If you have use cases that require high availability, there is no better solution than shared storage. But it is hard to compare the cost of SAN storage with the cost of local storage – so for SLA’s that are less demanding, it can have a very nice home.

    – Chris Midgley
    CTO, Unidesk (

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s


%d bloggers like this: