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Download a PDF of the Byte-Sized Book.
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I had the pleasure of contributing several passages for this book and I’m really happy to get it into your hands. This is GOLD!
PVS (and MCS) are amazing – but very often misunderstood – technologies. I have been in the reluctant camp with MCS (Machine Creation Services) mostly because of the huge impacts I have seen PVS (Provisioning Services) have on organizations workflow and performance. For many years the issue I find in the field is that people tend to focus completely on Storage performance with these technologies.
I won’t spoil this for you. Storage is a minimal impact compared to the more modern ability to cache in RAM. RAM of the OS is always… ALWAYS faster than your storage can ever be. So while I do hold that Hyperconverged infrastructure does wonders for improving MCS (which has since the beginning suffered from poor read speeds and very poor deployment speeds) nothing improves performance like even a small amount of RAM caching.
But MCSIO (the caching in MCS) is unstable, you say… Only if you don’t give it enough to work with and don’t properly defragment your system. As I found in recent cases you’ll get better results spending on RAM than storage… but let’s not jump too far ahead.
This is a teaser article for Chapter 4 of the Citrix Hero Program.
The chapter given to the current subscribers is 19 pages, nearly 7000 words of content. What you see here is more of the “WHY” not all of the how. But I didn’t want to leave you completely out in the cold. So I’ve included some links and other content that I hope will be helpful to you.
So what is the Citrix Hero Program?
Each month we tackle a new leading practice and dive in deep to make sure you understand it.
We have a live Q&A and video lessons to supplement the full chapter.
Members in good standing will have access to key past articles. This means that if you subscribe next month, you’ll get access to this full article right away!
Enrollment will re-open in April – I encourage you to try it out then to lock in a special price!
User experience suffers, especially later in the day. The problem seems to be worse for Machine Creation Services managed Server VDA hosted Desktops that are open all day long, however MCS Desktop VDAs seem to have similar symptoms. While not as high impact, a similarly configured Provisioning Services (PVS) target device exhibited similar symptoms. System pauses are experienced without subsequent CPU utilization spikes. While OS Optimization helps slightly the overall user experience seems to suffer regardless of how many programs are open. Workspace Environment Manager has helped memory and CPU issues but not solved the overall slowdowns issue.
The Administrators note that the problems do seem to increase with additional sessions being active, but cannot explain when the same amount of sessions at an earlier point in the day are not experiencing the slowdowns so they suspect that the number of sessions may not be the primary factor.
Storage Engineers are concerned as IOPS do increase toward the end of the day, but are still way below what the system is rated to perform. A recent move to an all-flash array has not had a noticeable impact so they have encouraged looking more at the programs themselves or that it is a ‘Citrix problem’. Network Engineers report no issues or notable differences between beginning and end of the workday.
This problem tends to be caused because either the Cache In RAM with Failover to Disk feature has not been configured or has not been configured with adequate RAM. So… increase the RAM cache if you are experiencing these slowdowns and see if that helps.
Additional Considerations:
Want to go deeper? Every month we take problems just like this and dive deep into the solutions in the Citrix Hero Program. Enrollment opens April 15th.
When PVS Target devices are configured properly (enough Cache, optimizations, etc) users are noting apparent lock-ups which clear after a few seconds. Programs are sometimes slow to load, especially early in the mornings. The problems are often much worse after new vDisk versions are deployed.
Monitoring the VDAs indicate no unusual CPU activity- in fact at the times users note issues, Administrators may note that there is little to no CPU activity. Event logs do not indicate any OS configuration issues that are related.
The Citrix team confirmed that caching, optimization and the above recommendations have been configured properly. By further troubleshooting they found that many VDAs are indicating high retries.
Network Engineers note there are no packet loss issues or utilization issues on the network (note- be careful here; I have seen would-be Citrix Heroes not accept this explanation and blame the Network, only to later be embarrassed by the real cause…)
One of the most common causes of Retries is actually the PVS server not being able to meet read requests rapidly enough. Most typically this is caused by inadequate RAM on the PVS Server. When vDisks are read Windows Server will automatically cache the data. This reduces reads from disk because the non-persistent VMs are always reading the same data. However, because the cache is FIFO (First In First Out) if the amount of reads exceed the cache, the PVS server must read from it’s vDisk Store. Even with very fast storage, seek times and transfer can cause delays.
Citrix has guidance on how to get started with proper RAM sizing for PVS (see below). A common misconception is that it would be better to have faster storage- in fact some customers use physical hardware or dedicated Flash-Based or RAM-Based storage only to find that the improvement is minimal. RAM is far cheaper a solution. We’ll discuss in far more detail in the main lesson.
Want to go deeper? Every month we take problems just like this and dive deep into the solutions in the Citrix Hero Program. Enrollment opens April 15th.
So- How do you resolve these issues?
Here’s a quick summary of what we cover in the rest of this lesson and some helpful links for you.
Want to go deeper? Every month we take problems just like this and dive deep into the solutions in the Citrix Hero Program. Enrollment opens April 15th.
Writing a book is… really hard. But what if you could easily help one be written?
Well, that is exactly the opportunity in front of you!
Instead of writing chapters, editing, more writing, more editing and then distribution, worry, stress and…
okay, I may be relating some personal experience here…
As I mentioned in my February Newsletter – You can participate in a unique project… by submitting just 250 words.
This is the collaborative effort of Christiaan Brinkhoff and Bas van Kaam – the Byte-Sized Book Project.
The question is – do you have something you’d like to say about Cloud design principles, leading practices or even recommended reference builds you’d like to relay to the world? This is your shot to be heard!
This is all about creating value for the community as a whole, but not asking for a ton from each person. I think it’s a brilliant approach!
So I encourage you to go for it! But don’t wait- the plan is to get the book edited and done in the next few months!
c’mon- 250 words is easy!
Learn a lot more detail here.
Support the project by going to https://www.bookprojectbytesized.com/ – Follow them on Twitter and spread the word!!!
THE IDEA BEHIND THIS PROJECT IS SIMPLE, WE ARE LOOKING FOR AS MANY CLOUD DESIGN PRINCIPLES, BEST OR COMMON PRACTICES, QUOTES, AND ARCHITECTURAL RECOMMENDATIONS AS POSSIBLE. FOR THE COMMUNITY, BY THE COMMUNITY!
“DJ, why are you giving away your best Citrix Tips?”
This question was asked of me recently- and I didn’t hesitate to give an answer. So I think I’ll give it to everyone here as a kind of open letter to the Citrix community…
It all has to do with quantity. I seem to give out the same things almost every week, not only in conversation but in my consulting engagements as well (regardless of if I’m representing Citrix, a Reseller or my own consulting company). So I asked myself two questions:
Before I get into this behind-the-scenes look (or if you don’t really want to know why, you just want my Top 3 tips right now) – click here to register for my free eBook where I give you those and put you on a monthly newsletter with even more tips – free:
The goal of this series is to outline some of the more common Citrix Mistakes that I have been seeing in my consulting engagements. These top three were chosen not because of frequency per se, but for the sheer impact they have. I chose them so that when you implement the fixes – you can be the hero. The #CitrixHero.
