I often sit with customers today and one statement I hear myself saying again and again is “do you have a desktop or application problem?” The point I am trying to highlight is that maybe we can solve the issue they have raised by pulling out the applications that require attention.  And not look at reworking their desktop strategy. After all it’s the apps that are important?

Recently I found myself again pondering this scenario and so I tweeted “It’s all about the apps, always had been always will be” and this generated a number of responses.  The first that came back was from @bramwolfs “I think it’s all about the data not specifically the apps..” Which immediately had me thinking there was little way out of this; data exists and is manipulated by apps, my focus has always been on the apps and that is where I make my money so that is where I placed my bet.  @KBaggerman highlighted a blog post titled “VDI OK What’s Next” by Stephane Thirion a Citrix CTP (@archynet) talking about desktops versus applications and applications versus data.  He makes some interesting points about the relationships between data and applications and the importance of data.  I can only agree however I would add that as some apps sole purpose is to collect and create data it is hard to define and almost irrelevant to consider which came first or which is more important, both are a requirement.

More interestingly he talks about user habits and the requirement of a desktop operating system, he also talks about the rise of mobile apps or micro apps; i.e.  apps created for a single purpose that do not require interaction or workflows with other applications and therefore do not require a desktop operating system.

This to me is an interesting area of development and I believe we are seeing two forces at play; the rise of SaaS and its adoption and the influence of the iPad and tablet.  Firstly SaaS is entering every workplace, I was recently  hosting a CIO round table discussion and every CIO was focused on SaaS and in fact the most interesting comment was “every app I deliver I now have to compete against a SaaS app, that is the way I have to think.” And you know what I think he was right; if you enforce a monolithic set of apps onto a workforce and it is not meeting the needs of a business unit then you can bet within days that business unit will be hunting out an alternative and swiping their credit card when they find something they like. Secondly the iPad factor, all apps on the iPad have single functions, I book my travel, check my email, look at website and knock over blocks with very upset birds.  Each app performs well and every day I use them I am breaking the habit of having to work within an operating system.  And therefore every day that operating system becomes less relevant to me.

Can we drop the operating system, no there are too many applications built for that platform. Is the desktop operating system becoming less relevant, yes however this has to be taken into context, just take a look at how many Windows 7 licenses have been sold since release.  But I do think that the mico app aided by the choice and availability on offer from SaaS vendors is accelerating change.

UPDATE  If you want  to read some interesting points head back to  “VDI OK What’s Next” by Stephane Thirion and join in or have a read.

Citrix Provisioning Server (PVS) is now at version 6.1.  Released in version 6.0 was the vDisk Update Manager and I think it is worth some time looking more closely at this feature.

When sizing VDI-in-a-Box there are four main considerations; disk space, disk speed, RAM and CPU.  I will look at each and discuss its potential impact.  All calculations come from Citrix eDocs guide; VDI-in-a-Box > VDI-in-a-Box 5.0.x >   System Requirements for VDI-in-a-Box 5.0.2 or are referenced via link.

Disk Space

Calculating disk space requirements will depend upon your hypervisor and the number of images you intend to utilise.  In the calculations below I have assumed that XenServer 6.0 with Thin Provisioning is utilised and that 2 images will be required for 2 desktop types, power users and normal users.

Fixed items will be the storage required for the hypervisor and the vdiMGR appliance, plus Citrix recommends reserving an amount for swap and transient activity. In the Dell and Kaviza reference architecture they recommend 100 GB.  Therefore, in this instance, fixed storage will be:

8 GB for the hypervisor + 74 GB for the vdiMGR appliance + 100 GB for swap and transient activity

=182 GB

For the desktops images, templates and virtual desktops, we will assume we are using non-persistent desktops, that we require 2 images and that the base image size is 20 GB for both desktop types.  VDI-in-a-Box uses 2 times the image size, to maintain multiple images, and the cloning technology uses 15% of the original size of the desktop image for each desktop created.  Therefore if we require 100 desktops the desktop storage requirement per host will be:

2 * image size * number of images +  # required desktops *(15% of image size)

= 2 * 20 GB * 2 + 100*(15% of 20GB)

= 80 GB + 100 * 3 GB

= 80 GB + 300 GB

= 380 GB

I recommend adding addition space for growth; in this instance I will assume 30%.  Therefore total disk capacity requirements will be:

Fixed items + desktops + growth

= (182 GB + 380 GB) + 30%

= 562 GB + 167 GB

= 729 GB

Disk Speed

Disk speed is all about IOPS, understanding desktop IOPS is an art in itself.  There are a number of main areas of consideration; boot IOPS, login IOPS, average use or normal operation IOPS, application launch IOPS and log off IOPS for the user type (e.g. normal or power user).  A good guide to IOPS considerations and measurements has been written by Jim Moyle titled “Windows 7 IOPS for VDI a Deep Dive 1.0”

In my example  IOPS numbers should be seen as a guide only to assist you in determining the disk speed required for your deployment.   The fastest disk is not always the most economical, therefore once you have determined the IOPS required it is worth looking at different options for your hardware based on capacity versus unit cost.

In this guide I have referenced the Citrix blog article “Finding a Better Way to Estimate IOPS for VDI”.  This is by no means a definitive guide however the section I have utilised “Calculating Workload IOPS” has a useful sub-section on user definitions and a recommended “ballpark guesstimates” figure for IOPS per workload.  By utilising these numbers I have been able to simplify my calculations and focus just on this number and not the boot and login numbers. The user definitions are listed below:

Light user: ~6 IOPS per concurrent user. This user is working in a single application and is not browsing the web.

Normal user: ~10 IOPS per concurrent user. This user is probably working in a few applications with minimal web browsing.

Power user: ~25 IOPS per concurrent user. This user usually runs multiple applications concurrently and spends considerable time browsing the web.

Heavy user: ~ 50 IOPS per concurrent user. This user is busy doing tasks that have high I/O requirements like compiling code or working with images or video.

Therefore in this example if we require 100 desktops, made up of 25 power users and 75 normal users our “guesstimate number” for IOPS will be:

(# of power users * 25 IOPS) + (# of normal users * 10 IOPS)

= (25 * 25) + (75 * 10)

= 625 + 750

= 1375 IOPS

Please note: to gauge a true reflection of required IOPS I would suggest monitoring the current usage patterns and workloads in your environment.  To bring the peak IOPS requirement down consider the start-up and login patterns and how these can be managed; e.g. allowing for a longer boot time and starting the boot process overnight or early in the day or by only allowing users to log off desktop not reboot and decide what you want to happen to desktops when a user does log off.

RAM

RAM requirements are an easier calculation to make however we still have to make a number of assumptions.  Total RAM required will be the RAM required for the hypervisor, plus the RAM required for the vdiMGR appliance, plus overhead, plus the RAM required for the virtual desktops.

Citrix recommends at least 1.5 GB for Windows 7 and at least 0.5 GB for XP, with 1 GB for the hypervisor, 1 GB for the vdiMGR appliance and a 10% overhead.

I have made the assumption that all my desktops are Windows 7 and that a normal user requires 1.5 GB RAM and a power user 2 GB RAM.  Therefore in this example the total RAM required is:

RAM for Hypervisor + RAM for vdiMGR appliance + (#power users * 2) + (#normal users *1.5) + 10%

= 1 GB + 1 GB + (25 * 2) + (75*1.5) + 10%

= 2 GB + 50 + 112.5 + 10%

= 164.5 + 16.45

= 181 GB RAM

CPU

CPU is similar in terms of RAM requirement in that we need CPU for the hypervisor, the vdiMGR appliance, overhead and virtual desktops.  The amount of CPU required per user type will vary, in my example I will only be assigning 1 vCPU per desktop however I will make the assumption that I will get less power users per core.  Definitions vary; Citrix eDocs states 10 for task workers, 8 for knowledge workers, and 6 desktops per core for heavy users and the Dell reference architecture states 5 for basic users and 6 desktops per core for standard users.

In my example I have picked an average and will assign 8 desktop per core for normal users and 6 desktops per core for power users. Therefore the total CPU requirement is:

1 CPU core for hypervisor + 1 CPU core for vdiMGR appliance + (# power users/6) + (# normal users/8)

=1 + 1 + (25/6) + (75/8)

= 2 + 4.1 + 9.3

=17 CPU cores (Rounded up)

Total Recourses Required

In my example I have 100 users in total of which 25 are classed power users and 75 normal users.

Each user will be supplied with a Windows 7 virtual desktop with 1vCPU, however normal users will receive 1.5 GB RAM and power users 2 GB RAM.

In total I will require:

• 792 GB of disk space
• 1375 IOPS
• 181 GB RAM
• 17 CPU cores

Choosing your Hardware Configuration

Considerations

There are a number of considerations we need to take into account when selecting hardware.

The first we need to discuss is availability.  Server class hardware is great however I do not like the idea of 100 desktops not being available, therefore for my example I am going to suggest an N+1 strategy.  This will always depend upon risk vs. expenditure and ultimately needs to be a business decision.

Secondly we need to think about type of hardware, disk type speeds and RAID configuration.  As all resources are on a single appliance and we need IOPS and disk space, in most instances blade configurations will be out of the question, as we will only have two disks.  Therefore we are often looking at a 2 – 4 U server.

In regards to RAID configuration, RAID 0 will give us maximum disk capacity and IOPS availability but may make us nervous about availability, leaving RAID 1 + 0 as the option that gives us disk space and availability without too much penalty.

Finally we need to consider disk seep as IOPS availability is important.  Citrix’s VDI-in-a-Box sizing guide states the following disk speeds

• SSD = 6000 IOPS
• 15K = 145 IOPS
• 10K = 125 IOPS

And Wikipedia states the following:

• SSD = 5,000 – 60,000 IOPS (SATA)
• 15k = 175 -210 IOPS (SAS)
• 10K = 140 IOPS (SAS)

In my calculations I have selected a middle ground and used the following:

• SSD = 6,000 IOPS
• 15K = 175 IOPS
• 10K = 125 IOPS

Hardware Options

The two figures that stand out for me in total resources required are IOPS and RAM.  See example below for a basic server configuration (Host Specifications):

In the example above, Table 1, a server with 16 cores, 96 GB of RAM and 8 x 15K SAS spindles in a RAID 1 + 0 configuration  can support 25 power users and 56 normal users based on my previous calculations and assumptions.  And as you can see it is the IOPS that restricts the number of power users and RAM that restricts the number of normal users.

In Table 2 below if we increase the RAM to 128 GB the number of power user desktops is still limited by IOPS however the number of normal user desktops is now also limited by IOPS.  Therefore if we had purchased a server in this configuration we would have been wasting money on RAM.  To take advantage of this amount of RAM we would either need to change the disk type or increase the number of spindles.

At no point in the two hardware examples has CPU cores or disk capacity been an issue.

The spreadsheet developed for these calculations can be found in the post on this site titled Citrix VDI-in-a-Box: Sizing Calculator.

Conclusions

Getting the hardware right is important and your number of servers will depend upon your appetite for risk plus your understanding of your environment.

Analysing your environment before you start to gauge IOPS is an important step.  The numbers here will help but can only be used as a guide.   Partners familiar with VDI-in-a-Box will have a good understanding of resources required and may be able to speed up this process based on their history of work.

Finally if you have completed some analysis just using some list price numbers on hardware you’ll see that by understanding your limit points, you can make sure you get the best return on hardware investment and reduce the overall cost per desktop.

It’s a long list and I’m sure yours is similar but why bother with it at all?  Well throughout this time I saw ASP to and fro, I built a lot of web servers for application web “e-projects”, I saw outsources come and go,  services were proposed on site and off site and  I was convinced we had the data centre of the future.  Yes during this time things were changing, processes were becoming slicker, application developers were becoming more sophisticated (I should clarify – Not in the sense that they stated wearing shoes to the office – just their programming skills) and capacity, in what we could do and what the programme, hardware or network would let us do was growing fast.  However through all that I was sure we had it licked Moore’s Law was in operation and we were taking full advantage of it.

In fact I still look back at those times and think I did good work and the teams I was part of helped the businesses we worked for grow, be more productive and transform.  And that for me this is the crux of the point I am trying to make, businesses do transform, it happens all the time.  Not all get caught up in the Innovators Dilemma, a GFC crash or a failed investment.  A lot grow fast; spin off in random directions and pioneer new industries.  However to do this today in an age where information moves fast, in fact where information is instant requires an agility a traditional environment cannot provide.

For a very simple example let’s take two IT executives that are required to roll out a new CRM system; the assumption is that their business has identified this need to help them reach new markets.  Meetings are held due diligence is completed and a project team is set up to identify the business requirements. Once identified team one brings in a global software provider, partners with a large technology provider and starts the process of developing the application and planning the roll out.  Team two picks a SaaS vendor and starts.  In this instance it is assumed that the SaaS vendor has a product that meets the business requirements identified during phase one of the project.  Is it that simple; well yes it is.  Both teams have completed the correct amount of due diligence to identify the business requirements and select an application  vendor, however team two does not have to build and roll out any infrastructure or mange the application, it just happens.  This means team two is delivering on the business outcome much faster than team one, enabling a competitive edge.

Okay now I can hear the outcries because you are an IT guy like me with an IT history like mine.  What about security, what about data protection what about lock in?  Well you know what, the business outcome has been met, the business is productive, competitive and happy.

I say job done and I say move out the way IT.

UPDATE 4/4/2012

Brett Winterford  of itnews  published an interesting article titled  Death of the SysAdmin with the following video clip of Fortescue Metals CIO Vito Forte, delivered during his keynote presentation at iTnews’ Executive Summit in Melbourne.  I think it summarise this article well.

Moving Ore and looking after the elderly present very different challenges when it comes to information management however all want to discuss VDI. In other words all think that VDI will meet a need in their business.  Some will argue that this conversation has been happening for some time and is nothing new, I can hear you yawning now and shouting: “its vendor push, its market hype, it can’t be done for less than a gazillion dollars, the user experience is rubbish and technically it’s too hard.  Come on people have been blogging about this for years, get with the program and write something about Big Data please!”

So why do customers keep coming back to the topic and where is the common value?  I believe the common value starts with the apps, all businesses run on applications.  It is applications that allow them to organise and process data into a meaningful product enabling the business to function.  Centralising apps, so all information can be processed in one place, i.e. all data is in one place makes a lot of sense.  So when I listen to organisations discuss their business needs it is applications we often come round to talking about.

The next stage with any customer is to trial and test our technology.  This means I get to spend time on site with my sleeves rolled up implementing products and integrating them into a proof of concept environment.   These days I just about always implement a NetScaler VPX for remote access, XenDesktop and XenApp.  At the end of every trial XenApp will have met the application requirements as discussed but it is XenDesktop that almost always has the customer most excited about their next desktop roll out.  If you get VDI right, then yes apps are as important as ever but virtual desktops is what the customer wants to do.  You cannot in my opinion underestimate the value of desktop virtualisation, the ability to rapidly deploy, enable a single user experience from any location and to give a user a desktop that is always available without carrying a device.

When I first started at Citrix, over 5 years ago, I had just about everything locally installed by IT on my laptop, this was then shipped to my remote office (home) and away I went.  All apps were available as hosted applications but for me Office was installed locally and everything else, e.g. SAP was hosted on Presentation Server.  I had device flexibility in that I could get to my hosted apps from any device with an ICA client but because of the way I worked remotely this rarely happened.

Things changed as our technology changed e.g. accelerated access to mapped drives was cool, improved performance of hosted apps was always appreciated and the new version of Office arriving streamed made a difference.   A difference in that I started to add additional apps to my local pool.

Then over eighteen months ago I decided to move my full working day into a virtual desktop.  I had been using XenDesktop before but not exclusively, I would chop and change between environments depending upon task.  But it felt like the right time to move so after a quick copy of a few files away I went.

The experience has been good for a number of reasons.  Firstly as a remote employee working from a home office, I never worry about mapped drives, centrally stored content or the device I am working from.  It’s not unusual to find me outside having pinched my wife’s Mac book working on a document in our garden; it’s a pleasant place to be and my laptop stays docked.  As I navigate through tasks launching multiple applications the interaction is familiar and easy and from a user experience point of view I have few complaints.

Do I still use my local device, sure over the year and a half I have dropped into a local browser to run video content and a presentation or two.  Outside of that it’s really the personal stuff that I use locally, I access Facebook via my local browser, I have a local Twitter client and Skype for family calls when I am away.  My work desktop is thousands of kilometres away and to be honest I’m keeping it that way.

I visit server rooms and data centres on a regular basis and it is becoming common for these to be described as company X’s cloud.  However if the environment has been built using the same principles and architecture as the last data centre then the environment will never scale correctly or offer services the way a true cloud can.

Sheng Liang outlined five areas of consideration:

1. Enterprise architecture scales up server clusters, cloud architecture scales out server farms
2. Enterprise architecture assumes reliable infrastructure, Cloud architecture expects infrastructure to fail
3. Enterprise architecture is high cost, Cloud architecture is low cost
4. Enterprise architecture is IT Mgmt-centric (1:100′s), Cloud architecture is autonomic management (1:1000′s)
5. Enterprise architecture uses proprietary vendor stack, cloud architecture uses open, value added stack