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Xendesktop slow typing and frequent gray screens.

Posted on 2014-02-22
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Last Modified: 2014-03-08
I'm trying to troubleshoot a small Xendesktop 7.1 deployment.  Users are getting
frequent gray screens (re-connection from session reliability) up to 10 a day and randomly when typing the text is about 2-3 words behind.

Same users who connect to a terminal server and run the same programs do not have either issue. Many times these users are working right next to each other and only the VDI
desktop user is affected.

This seems to only occur on users who connect to a non persistent Win7 VDI desktops. The specs are very high on each desktop and things seem to run pretty fast until you start typing but even then its only random, happening about 70% of the time.

This issue is driving me crazy. I have examined event logs on the virtual desktop and the Xendesktop controller. I have tried migrating the effected machines onto different ESX hosts (both ESX 5.1 and 5.5) and different storage tiers on the EMC SAN. No luck.

I disabled GPU acceleration in Office 2013.
I have checked storage latency. All OK.
I have verified it is not an internet connectivity or latency issue.
I have applied the default WAN optimized template to the delivery group in Citrix Studio.

Not sure what else to check. I am still very new to Xendesktop 7.1 and would appreciate any recommendations.
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Question by:ubixtech
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by:Busbar
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can you shed more light on the setup, what are the VMs specs and what are the hypervisor you are using.

Also, is this infra done via PVS or MCS, do you have director installed, because director will shed some light on latency and connection trends, thus I highly recommend installing it.

are you using roaming profiles, can you try with regular profiles ?!

meanwhile, I don't think it is network, I think it is hypervisor or storage performance issue.
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by:ubixtech
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Busbar,

The Windows 7 VM's have 2-4 GB on Ram and 2 vCPU. They were created using PVS.

Hypervisor is VMWare ESX 5.1 and 5.5.

Roaming profiles are being used. Remember this is not a problem for the same user
who connects to a Citrix Terminal Server and is still using roaming profiles. Only happens to VDI desktop users.

I will put in a request to have Director installed. Does it require a lot of resources and configuration?
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by:Busbar
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for the director no it is not.
I think I know where is the issue, where did you configure the write cache, on the server ?!
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by:ubixtech
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I am not sure what you are referring to? The page file of the VDI desktop?
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by:Busbar
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read this: http://support.citrix.com/article/CTX119469
by default it is on the server, so you might be overwhelming the server. first try configuring it on RAM to see how things are .
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by:ubixtech
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Sorry we are using Machine Creation Services not PVS, I was mistaken. Does that make a difference?

I don't think vdisks are used because the desktops reset back to the golden image after a reboot.
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by:Busbar
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no worries.
can you share with me the HW specs of the hypervisor and underlying storage, can you configure the VMs with 1 vcpu and see the difference.
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by:compdigit44
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Have there been any changes to the environment lately either hardware or software?
Are all VDI clients having the issue on the same subnet?
What build of XenDesktop are you using?
What Citrix Receiver version are your clients using?
Is there any type of AV or security software running on the clients / server?
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by:ubixtech
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Some of the VDI desktops only had 1 vCPU previously but were upgraded to 2 and still exhibited the same issue.

The Hypervisors are DL380 G6 proliant  Quad Xeon cpu's with 1/4 TB of RAM. The hardware has very low utilization. Connected to Cisco catalyst switches (1 Gbe) and Cisco ASA firewall.

Latest version of receiver (Late 2013) on clients.
VDA Version 7.1.0.4033
Xen Desktop  7.1  (11.11.1 build 13012 from the licensing page)

We are using Viper AV on the servers, but disabled it for periods of troubleshooting and the problem still exists.

What really gets me is the fact that it only effects VDI users and not users who are connecting to a server OS.
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by:Busbar
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install Xendesktop director and let us see if there any findings...
what about the SAN, are you using NFS or block storage ?! have you seen any hits ?!
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by:ubixtech
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Director just shows connection details and statistics. I didn't see anything that would
indicate quality of service. Then again I am not really familiar with that tool.

SAN is using block storage only. I verified with EMC that the load on the spindles were low.

One thing that we are thinking of is the Windows 7 VM template we used maybe screwed up in some way. I am going to test it out by building a new VDI Virtual Machine. Anyone have any recommendations for optimizing Windows 7 template for VDI use?
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by:compdigit44
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I may have misread you post but are your servers connected to your SAN via a 1GBe connection?

Are you using FC or iSCSI for your SAN connection?
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by:ubixtech
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No Fiberchannel is used. This is a small environment.
Connectivity to SAN is 4x 1 Gbe connections using iSCSI.
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by:compdigit44
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It sounds like that is your problem...

The 1GBE connection to your SAN is to slow!!!!
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Busbar earned 500 total points
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I agree, to some extend, 4 GB in port channel could be fine, but it depends on how you configured your network, did you separate data from IO traffic, do you have dedicated iSCSI switches and using iSCSI NICs on the servers or using normal cards, iSCSI is tricky and mean.
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by:ubixtech
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They have separate VLANs for storage for SAN so its isolated. I still don't see how it might be
storage related since terminal users do not have this issue, ever. Is there a tool or test I can from the users desktop to get session statistics, especially IO. I tried perfmon and it wasn't very user friendly and didn't show any Citrix related details.
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by:compdigit44
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You storage vendor should have such tools in there management console..
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by:ubixtech
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Using Citrix Director was a good suggestion to address other session quality issues but the delayed typing problem still persists.

We ended up enabling this policy on a test group and it seemed to speed things up and decrease the gray screening but not eliminate it completely. http://support.citrix.com/proddocs/topic/xendesktop-71/ps-ref-policies-graphics.htm
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