Any Citrix Guru's out there???

[Incognito]

We are having performance issues and we are not getting any detailed technical info back as to what the potential problems could be.

If it's performance related and it's virtualised I'd say 7 times out of 10 it's bad storage design. People don't appreciate storage contention and think as long as they have enough disk space then they're fine, but if you have 500 GB of data spread out over two 250 GB disks, you're going to have more issues than if you have 500Gb of storage spread out over five 100 GB disks. That's very, very basic stuff. You size enterprise Virtualisation deployments by number of spindles you're presenting at the back end. You don't really worry about the amount of storage you have to present, just the number of spindles you have to present that will be able to guarantee your required I/O (because the second method should always result in a larger amount of storage being presented than the first).

Read:

Storage Basics – Part I: An Introduction | VMtoday

and then:

Storage Basics – Part II: IOPS | VMtoday

If you post the answers to the questions in my previous post I should be able to point you in the right direction.

[original PM]

Once again many many thanks!

It's not that we do not have faith in the designer.

We are having performance issues and we are not getting any detailed technical info back as to what the potential problems could be.

So we are having to look elsewhere to confirm that they are building and managing the servers and resoruces correctly.

It's a sad state of affairs when you consider it is not outsourced but is all internally hosted.

[Incognito]

yes further investigation tells me that we are using XenApp

so what areas would be best to investigate??

Cheers!!

Who's doing the investigating? Sounds like you don't have faith in your designer.

Couple of links

Virtualize XenApp « Virtualize My Desktop

Virtualization Best Practices for XenApp | Citrix Blogs

But to be honest, if your systems not scaled correctly anyway, no amount of config changes will improve anything.

What's your environment? ESX, Hyper-V, XenServer
Storage? Shared storage (SAN) or Local (disks on server)
Size of storage?
Storage contention? (If local, number of VM's per Raid group, if SAN number of VM's per LUN) *If you are using a server with local storage advise how many disks are in the box and how they're set up i.e. Raid 5 etc
Number of VM's
Host specs - CPU, Mem (host is the hypervisor, i.e. ESX etc)
Guest specs - CPU, Mem (guest is the VirtualMachine)

[original PM]

yes further investigation tells me that we are using XenApp

so what areas would be best to investigate??

Cheers!!

[JoJoGabor]

Can you confirm if it is Xendesktop and not XenApp?

I do VDI nearly all the time, if its runnign like a dog, the usaul cause is the SAN the virtual desktops are running off. Check the datastore latency in vcenter (IF VMware) if Xenserver, I cant remember. Latency should not be peaking over 40ms.

Its not unusual for badly performing systems for this to reach hundreds of ms, the worst I saw at a big bank was 1900ms! 19seconds to get a disk reqeust back!

[original PM]

cheers Dave B much appreciated

[DaveB]

Cheers Incognito!

Can you just clarify what the role of the hypervisor is and what options are available.

As yes it is running like a dog at the moment!

The Hypervisor manages the resources for the VM's under it's control on a particular physical box or cluster of boxes.

If you have one physical server running multiple VM's to serve up client sessions then the Hypervisor is where you configure those VM's and assign memory, disk, processoer resources to each VM. This, as has been said, is all an overhead on the box it's all running on.

As for options you can

a. Not run VM's on the box and allow all the Citrix sessions to be run under one server instance. This will free up those resources being used to run the hypervisor and manage all the VM's. Downside is an increased risk of losing service for every session rather than just those on one VM if anything goes wrong at the software level, but physical failure is probably more of an issue and that will kill all your VM's if it happens anyway as it's all on one box.

b. Add more memory/disk/processor to the current box. Will improve performance but costs money.

c. Combine a + b.

d. Add another box or boxes and cluster with the existing one under the same Hypervisor and give all your VM's some more resource. Will improve performance and resilience more than option b. Down side is an increase in complexity at the cluster / Hypevisor level and cost implications.

[stek]

Cheers Incognito!

Can you just clarify what the role of the hypervisor is and what options are available.

As yes it is running like a dog at the moment!

The hypervisor is what doles out the physical resources to the VM's. Is it ESX for some other intel-based solution? Not really my area tho - I do Unix virtualisation on IBM pSeries, different beast...

[original PM]

Cheers Incognito!

Can you just clarify what the role of the hypervisor is and what options are available.

As yes it is running like a dog at the moment!

[Incognito]

If you're talking about XenDesktop and controller placement, then you need to factor in availability. If you only have one physical server and it goes down then you lose the service. However, if you have it virtualised at least you can rely on the HA from the technology below. Also reduces cost if you want to scale out.

You are correct in thinking it does take up resource on the box though. However from how you've described it, it sounds like you have everything hanging off the back of a single hypervisor. It's certainly plausible if sized correctly if you're just wanting to do it for a POC, if not then it'll run like a dog.

[original PM]

Hi All,

Bit of a technical query. (and apologies if my understanding of the technology is a bit flaky!)

When running a citrix environment to present a virtual desktop to a user is it a good idea to split your physical servers into a number of virtual servers or does the fact you are running virtual servers take up some of the resources of the physical server and therefore you have less resources available to present the desktop to the user?

If to give a meaningful answer you need more info please ask!!!

Cheers!!!