Posts Tagged ‘XenApp’

Tolly Group releases another Citrix vs. VMware comparison

April 15th, 2009

A few months ago, The Tolly Group released a report comparing Citrix and VMware VDI solutions.

They’re at it again. Today, The Tolly Group released another comparison. Today’s report compares Citrix XenServer 5 and VMware ESX 3.5.0 Update 3 with Citrix XenApp as the workload.

Citrix Systems commissioned Tolly to evaluate the performance of Citrix XenApp when running on Citrix XenServer 5 and compare that with XenApp running on VMware ESX 3.5u3.

Testing focused on system scalability and user quality-of-experience. This test report was approved for publication by VMware. The VMware End User License Agreement (EULA) requires such approval.

The testing was conducted in accordance with Tolly Common RFP #1101, Virtual Server Performance.

Summary of Results:

* Citrix XenServer 5 outperforms VMware ESX 3.5 by 41% in user scalability tests.
* XenApp, running on XenServer, retains a consistent user experience as load is increased to 164 users.
* Virtualizing 32-bit XenApp gives IT administrators a viable approach to increasing total user density on physical servers, without the need to re-certify their existing applications and drivers for a 64-bit platform.
* Consolidating XenApp farms on XenServer results in data center reliability benefits and cost savings.

Click here to download the report. You will need to register for the report download.

Rapid Virtualization Indexing (RVI)

March 8th, 2009

I’m mildly excited for the upcoming week. If all goes well, I’ll be upgrading to AMD Opteron processors which support a virtualization assist technology called Rapid Virtualization Indexing (or RVI for short).

There is overhead introduced in VMware virtualization via the virtual machine monitor (VMM) and comes in three forms:

  1. Virtualization of the CPU (using software based binary translation or BT for short)
  2. Virtualization of the MMU (using software based shadow paging)
  3. Virtualization of the I/O devices (using software based device emulation)

RVI is found in AMD’s second generation of virtualization hardware support and it incorporates MMU (Memory Management Unit) virtualization. This new technology is designed to eliminate traditional software based shadow paging methods for MMU virtualization thereby reducing the overhead in bullet #2 above. VMware lab tests show that RVI provides performance gains of up to 42% for MMU-intensive benchmarks and up to 500% for MMU-intensive microbenchmarks.

How it works:

Software based shadow page tables store information about the guest VM’s physical memory location on the host. The VMM had to intercept guest VM page table updates to keep guest page tables and shadow page tables in sync. By now you can probably see where this is going: applications and VMs which had frequent guest page table updates were not as efficient as those with less frequent guest page table updates.

The above is similar to guest VM kernel mode calls/context switching to access CPU ring 0. Previously, the architecture wouldn’t allow it directly via the hardware so the VMKernel had to intercept these calls and hand-hold each and every ring 0 transaction. Throw 10,000+ ring 0 system calls at the VMKernel per second and the experience starts to become noticeably slower. Both Intel and AMD resolved this issue specifically for virtualized platforms by introducing a ring -1 (a pseudo ring 0) which guest VMs will be able to access directly.

VMware introduced support for RVI in ESX 3.5.0. RVI eliminates MMU related overhead in the VMM by relying on the technology built into the newer RVI capable processors to determine the physical location of guest memory by walking an extra level of page tables maintained by the VMM. RVI is AMD’s nested page table technology. The Intel version of the technology is called Extended Page Tables (EPT) and is expected sometime this year.

One of the applications of RVI that interests me directly is Citrix XenApp (Presentation Server). XenApp receives a direct performance benefit from RVI because it is an MMU-intensive workload. VMware’s conclusion in lab testing was that XenApp performance increased by approximately 29% using RVI. By way of the performance increase, we can increase the number of concurrent users on each virtualized XenApp box. There are two wins here: We increase our consolidation ratios on XenApp and we reduce the aggregate number of XenApp boxes we have to manage due to more densely populated XenApp servers. This is great stuff!

There is a caveat. VMware observed some memory access latency increases for a few workloads, however, they tell us there is a workaround. Use large pages in the guest and the hypervisor to reduce the stress on the Translation Lookaside Buffer (TLB). VMware recommends that TLB-intensive workloads make extensive use of large pages to mitigate the higher cost of a TLB miss. For optimal performance, the ESX VMM and VMKernel aggressively try to use large pages for their own memory when RVI is used.

For more information and deeper technical jibber jabber, please see VMware’s white paper Performance of Rapid Virtualization Indexing (RVI). Something to note is that all testing was performed on ESX 3.5.0 Update 2 with 64 bit guest VMs. I give credit to this document for the information provided in this blog post, including two directly quoted sentences.

For some more good reading, take a look at Duncan Epping’s experience with a customer last week involving MMU, RVI, and memory over commit.

Where to get timely VMware virtualization information

December 25th, 2008

Happy Holidays!  I thought tonight was the night I was going to post some “Citrix XenApp virtualized on VMware ESX” that many have been asking me for behind the scenes, but alas it’s 10:30pm and I just don’t have the energy for such a post that will require considerable effort to put together.  I’ve accumulated some information here and there for various people, but it’s time to formally consolidate the scattered pieces of information into one decent post that I can fine tune as needed going forward.  Before you start licking your chops in anticipation of a rocket science blog post on virtualizing Citrix, please don’t.  What I promise is the details and discoveries behind one person’s virtualized Citrix environment.  With VI3, virtualizing Citrix is fairly straightforward but extra special attention must be paid in determining virtualization candidacy.

Now I wouldn’t want anyone to walk away empty handed from my blog on Christmas so I leave you with this:  A no-frills post revealing the source of where I get 90-95% of my daily virtualization information – RSS feeds of various blogs and websites.  This file (right click, save as – it’s XML) contains an export of all of my RSS subscriptions.  Import it into your favorite RSS reader.  Set your RSS subscription refresh interval to 15 minutes.  Stay informed with nearly up to the minute and late breaking VMware virtualization news.  With new blogs and sites popping up weekly, for sure this list is nowhere near what I would call complete.  If you have any suggestions or if you see a great blog or site that I am missing, by all means, let me know in the comment section below.  I’m the type of guy that can never get enough VMware virtualization information.

Disclaimer:  My RSS subscription list contains a few subscriptions to non-virtualization related feeds which you may want to remove.

Update:  I’ve added two more great blogs to the RSS feeds:  Gabe’s Virtual World (Gabrie van Zanten) and Jase’s Place (Jason McCarty).

VMware product name changes

December 3rd, 2008

Quick update on a news item you may have already heard about. Remember those VMware product/component decoder rings you might have started working on after the VMworld 2008 announcements? It’s time for an update. VMware announced a handful of product name changes on Monday:

  1. VMware VirtualCenter is now VMware vCenter Server
  2. VMware vCenter is the family name for all management products
  3. VMware Lab Manager is now VMware vCenter Lab Manager (since it is in the management products family)
  4. The VMware vCenter prefix applies to the other products in the management products family as well
  5. VMware View is the family name for all VDI/VDM products
  6. VMware VDI is now VMware View
  7. VMware VDM is now VMware View Manager

I’m not real fond of name changes unless there is a good reason behind it. I’ll give VMware the benefit of the doubt that there was good reason to make these changes, although not knowing myself 100% what is up VMware’s sleeve, the timing is somewhat debatable. Couldn’t they have waited until the next generation of Virtual Infrastructure to align the products and components? Citrix did this with Presentation Server when they instantly re-branded it to XenApp. It confused a lot of people, especially the newcomers. I hope confusion among VMware customers is minimized. It’s going to take a little while for these new names to become second nature for me.

What do you think of the name changes? Feedback is always welcomed here.

Brian Madden purchased by TechTarget

November 19th, 2008

No, a human being was not purchased like a head of cattle (at least let’s hope not). Brian Madden has been a well known mogul in the Citrix community for quite a long time and has been making a splash lately in the virtualization arenas (primarily virtual desktop infrastructure where Citrix products XenApp and XenServer compete for market share along with VMware, Microsoft, and others).

Brian Madden uses his personal name as his product brand to become successful in many of his accomplishments including public speaking, industry analyst, technical author, blogger, knowledgebase website, creator of the impressive annual BriForum convention, book publisher, etc.

Brian is a wealth of knowledge first and foremost. I’ve read a few of his Citrix/Terminal Services books and he ranks right up there at the top among the most knowledgeable authorities when it comes to Citrix and Terminal Services. I also regard Brian as an interesting character with a unique and funny personality. Read some of his blogs about his adventures and you’ll understand. A year or two ago I followed Brian over the internet as he sold his house and most of his possessions and became a world traveler with no place to call home except for whatever hotel he was in at the time. When he sold his house ‘n’ things, he hired entertainment for the kids such as one of those big enclosed hot air trampolines you’d likely see at a carnival. I think he had a popcorn machine, food, hired clowns, etc. All at his expense. Nobody does it quite like Brian.

TechTarget is an IT media company founded in 1999 that has 600 employees and went public in 2007. TechTarget writes “The Brian Madden Company brings the largest community of IT professionals specializing in application delivery and desktop virtualization.” In one transaction, TechTarget purchases an already existing and established fountain of knowledge that it can in turn use to help its clients. However, I’m not sure about the accuracy of the last part of their statement if you consider the virtualization leader, VMware, has built a virtualization community of well over 100,000 people from around the globe.

I wish Brian and TechTarget much success now and into the future.

Read more about the official announcement from TechTarget here.

Update: Brian’s official announcement at

VMware releases ESX 3.5 Update 3 and ESXi 3.5 Update 3

November 6th, 2008

On Thursday November 6, 2008, VMware rolled out an incremental update of its bare metal hypervisor and flagship product:

  • VMware ESX 3.5 Update 3 (build 123630)
    • vCPU per core limit raised from 8 (11 for VDI) to 20
    • Newly supported hardware
    • Newly supported guest OS
      • Solaris 10 U5
      • Ubuntu 8.04.1
      • RHEL 4.7
    • Interrupt Coalescing (IC) for Qlogic 4Gb FC HBAs
    • Experimental support for the VMDK Recovery Tool (a script that helps recover VMFS/VMDK from accidental deletion or corruption)
    • Updated Small Footprint CIM Broker to v1.3.0
    • IBM SAN Volume Controller (SVC) now supported with both Fixed and MRU fibre multipathing policies
  • VMware ESXi 3.5 Installable/Embedded Update 3 (build 123629)
    • vCPU per core limit raised from 8 (11 for VDI) to 20
    • Newly supported hardware
    • Newly supported guest OS
      • Solaris 10 U5
      • Ubuntu 8.04.1
      • RHEL 4.7
    • Interrupt Coalescing (IC) for Qlogic 4Gb FC HBAs
    • Updated Small Footprint CIM Broker to v1.3.0
    • IBM SAN Volume Controller (SVC) now supported with both Fixed and MRU fibre multipathing policies

VMware Infrastructure 3 Documentation is still referencing ESX as ESX Server which I don’t understand. VMware made it clear that the word “Server” was dropped from the bare metal hypervisor product many months ago. I guess name changes are easier said than done (except in the case of Citrix where Presentation Server customers might remember waking one morning and suddently everything on the website was called XenApp with no trace of Presentation Server left – talk about confusing.)

Head to VMware’s download site now