Virtualization - Cloud

Month: July 2017

PVS Streaming Service Abrupt Termination – Cache Change Mode Procedure for production vdisk


PVS stream service abrupt termination  intermittently (approx. once in month) which causing user sessions freeze and user unable to launch HSD’s.

Environment :

2 Citrix PVS Servers (VM’s) with version 7.6
2000-3000 concurrent  Users
86 HSD’s & 6 Golden Images
Microsoft Hypervisor 2012R2 ( 15 Node) – CICSO UCS


  • Issue occurring once or twice in a month and there is no common pattern in days or hours,issue recurring in both PVS servers at a time
  • No changes in environment
  • Onsite engineer informed that issue existed since 3 months and issue getting resolved post restart of PVS servers.
  • One day,  same issue repeated but issue not sorted out post restarting of PVS servers -> Issue escalated to support team (Me)
  • Observed  Event Id 11 :”Detected one or more hung threads , DbAccess error: <Record was not found> <-31754> (in ServerStatusSetDeviceCount() called from SSProtocolLogin.cpp:2903” -> Indicates “Thread hangs under the stream service” & DB Access errors
  • Observed multiple vDisk retries on the problematic target devices. 11 at boot time and approximately 611 per hour during session
  • Observed recommended MacAfee exclusions are not in place -> Stopped MacAfee service and restarted PVS server -> PVS Streaming service stable for some time on one PVS server  and again terminated ->Due to time constraint, logged a call with vendor(Citrix).
  • After 2 hrs, Citrix support joined the call and started collecting CDF races and procdump collection for the terminating stream service
  • After few hours , issue resolved automatically and Citrix support unable to find root cause with collected logs
  • In 2 months , issue repeated 2 times and customer frustrated as root cause was not found for abrupt streaming service termination intermittently.
  • Support Team (Myself) analyzed the environment and observed the Cache mode is configured as “ Cache on Server”  which is not recommended for Production environment , Best practice to use “Cache on RAM overflow to HDD”  which is a best practice to reduce load on PVS server & optimal performance ->Taken the same observation Citrix support and requested their observations

Explained to customer that missing of best practices will lead to these type of intermittent issues , since  there is no root cause found  and it is not a best practice to keep cache on server in production environment , prepared a plan to change cache configuration to” Cache on RAM overflow to HDD”.

Current PVS Storage configuration for cache as below

PVS1 (VM)->1700 GB allocated  through Virtual HBA ( Total golden Image Sizes is 440 Gb & Remaining for Write Cache)

PVS2 (VM) -> 1700 GB allocated through Virtual HBA ( Total golden Image Sizes is 440 Gb & Remaining for Write Cache)

Proposed Storage change Configuration as below:

Post referring multiple blogs, Write Cache proposed to all images(profiles) is 20 GB -> Therefore , for 86 HSD, 1820 GB required and it should present to complete Hyper-v cluster as HSD hosted on cluster.

Citrix-XenApp-XenDesktop-XenServer Servicing Options

Citrix provides servicing options to give greater flexibility and choice in how to adopt new XenApp, XenDesktop, and XenServer functionality while giving greater predictability for maintaining and managing the support of your environment

Last year, Citrix introduced two new XenApp / XenDesktop servicing options, the LTSR, which stands for Long Term Service Release and the CR a.k.a. Current Release., In 2016, Citrix announced first LTSR of XenApp and XenDesktop 7.6 and in 2017 first LTSR for XenServer 7.1 that is available for download on

What is LTSR?

As a benefit of Software Maintenance, Long Term Service Releases (LTSR) of XenApp ,XenDesktop,XenServer enable enterprises to retain a particular release for an extended period of time while receiving minor updates that provide fixes, typically void of new functionality. Long Term Service Releases (LTSR) is ideal for large enterprise production environments where you would prefer to retain the same base version for an extended period

A Long Term Service Release guarantees 5 years of mainstream support and an optional 5 years of extended support (needs to purchased separately). This includes cumulative updates every 4 to 6 months, a new LTSR version of XenApp / XenDesktop every 12 to 24 months and any potential (hot) fixes

A valid Software Maintenance (SM) contract is needed to make use of the LTSR or CR servicing option.

Ideal customer environment for a LTSR is for the customers who typically follow a 3-5 year version upgrade cycle

Long Term Service Releases will have a regular cadence of Cumulative Updates that will typically contain only fixes

What is Current Release?

Any new release of XenApp/XenDesktop/XenServer will be labeled a Current Release. With the CR servicing option you can always make use of (install) the most recent XenApp and/or XenDesktop versions including all the latest enhancements and additions that come with it.

Its release cycles are much shorter with a new version release being announced every three to nine months in general.

Citrix recommends that large enterprise customers have a combination of Current Release and Long Term Service Release environments.

Switching from a LTSR to a CR servicing, and vice versa, is always optional as well

All initial releases of XenApp/XenDesktop/XenServer will be a Current Release. There will likely be multiple Current Releases of a major XenApp/XenDesktop/XenServer version (i.e. 7.6, 7.6 FP1, 7.6 FP2, 7.6 FP3, 7.7, 7.8 ,7.9,7.11,7.13,7.14); however, there will likely only be one LTSR release of that version after that release is considered customer-tested and industry-proven (i.e. 7.6 FP3).

How will the customer know if their environment is Long Term Service Release compliant?

Citrix support and engineering have developed the LTSR Assistant tool which will scan your environment and compare your environment with the necessary LTSR components to determine if you are compliant. The tool provides a report that will outline the necessary updates to achieve compliance. The LTSR Assistant tool is available for download at

Will a customer running an LTSR compliant environment be supported if they also have non- compliant components?

Citrix does not recommend mixing non-compliant components. For example, if a customer decides to implement Provisioning Services 7.7, which is not compliant with the current 7.6 LTSR environment and the customer has an issue with Provisioning Services 7.7 the customer may be asked to move to the latest Provisioning Services Current Release to receive public fixes

How often will Citrix release a Long Term Service Release of XenApp and XenDesktop or XenServer?

Citrix will release a Long Term Service Release of XenApp and XenDesktop or XenServer based on the number of features, implementations, customer support cases and general feedback. However, as very general guidance it can be expected that Citrix will release a new Long Term Service Release every 12-24 months; however, Citrix reserves the full rights to alter those timelines.

Is Citrix discontinuing the process of providing Hotfix Rollup Packs (HRP) for XenApp and XenDesktop?

With LTSR, Cumulative Updates will replace Hotfix Rollup Packs (HRP). Hotfix Rollup Packs (HRP) will still be made available for XenApp 6.5.

Will 7.6 LTSR support XenApp for Windows Server 2008 R2 for 10 years?

Windows Server 2008 R2 will not be eligible for extended support. Citrix will continue to monitor Windows 2008 R2 lifecycle dates for future determination of lifecycle milestones.



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