Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17


Difference between personal vDisk and Write cache drive in Citrix XenDesktop, using PVS?

Posted on 2014-01-26
Medium Priority
Last Modified: 2014-01-29
Hello there,

What is the difference between personal vDisk and Write cache drive in Citrix XenDesktop, when using Provisioning services.

For example do we need to have 2 x locally attached drives for each XenDesktop for write cache and Personal vDisk?

Please advise.

Thanks and Regards
Question by:goprasad
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 5
  • 3
LVL 37

Expert Comment

by:Carl Webster
ID: 39810852
Write Cache is where the difference stuff is kept and also where you can put persistent stuff like event logs, antivirus definition files and any other item(s) that need to persist between reboots of the desktop/vm.

PvD is where user personalization and user installed software goes.

You need to have two extra drives attached to your master image.

The write cache drive needs to be formatted and assigned a drive letter.

The PvD drive needs to be initialized but NOT formatted or assigned a drive letter.  The PvD drive gets handled by the PvD part of the VDA and is assigned a drive letter when you run the XenDesktop Setup Wizard.

I am writing an article on this very topic as we type.

Author Comment

ID: 39810898
WOW - Brilliant explanation.

Which means - as I am planning to use PVS to stream desktops, I will need to provision 2 x locally attached drives at hypervisor level,

 - If I assign drive letter D:\ for write cache - this needs to be formatted and can be thin provisioned.

- For personal vdisk - this gets handled when I run XenDesktop set-up wizard.

I was getting confused with following explanation of PVD : wherein I thought that write cache drive is provisioned within PVD.

By default, when you create a PvD, no matter the initial size, it will split the disk equally between User Profile and Applications.  E.g. if you have a 10GB PvD, 5GB will be for User Profile, Data, Docs, Personalisation etc. and 5GB for user installed applications.
LVL 37

Expert Comment

by:Carl Webster
ID: 39810912
In my testing, the Write Cache drive is always set as Drive D.  That is why I recommend moving the CD drive letter to like Z.

Create your Write Cache drive, format it and assign it Drive D.  That way your image (and future images) "know" there is a drive and since PVS/XD will make the drive D go ahead and do everything with it set as D.

I do not recommend doing anything as thin provisioned except in a lab.  You MUST make sure you have the space to handle all the space you have provisioned to be used so why not make everything think so you are not caught by a surprise during a peak usage time and everyone is breathing down your neck!!!

Yes, everything about PvD gets handled by the XD Setup Wizard and the PvD software.  If you are using XD7.1 make sure to update to PvD 7.1.1 BEFORE you do anything with it.

You are correct on the PvD split.
Get free NFR key for Veeam Availability Suite 9.5

Veeam is happy to provide a free NFR license (1 year, 2 sockets) to all certified IT Pros. The license allows for the non-production use of Veeam Availability Suite v9.5 in your home lab, without any feature limitations. It works for both VMware and Hyper-V environments


Author Comment

ID: 39810929
One last clarification: Is my calculation correct?

for a 300 user base for XenDesktops
- Master Image (base Win 7 32 bit OS plus core apps) - 25 GB
- Write Cache drive 25 GB x 300
- PVD 10 GB x 300

Therefore total disk space: 7500 + 3000 = 10.5 TB

Please advise.
LVL 37

Accepted Solution

Carl Webster earned 2000 total points
ID: 39810946
A 10GB write cache drive will be enough for a desktop that is rebooted once a week.  25GB is WAY overkill.

The PvD sizes I have worked with have been 20 to 30GB.  It all depends on whether you are using profile mgmt software or not, are you redirecting folders and how much software will users be installing.

There is one master image - 25GB.
300 10GB Write Caches drives is 3TB
300 10GB PvDs is 3TB

Total space is barely over 6TB.
LVL 37

Expert Comment

by:Carl Webster
ID: 39810947
Oh, I forgot.  To make your life MUCH easier, do not have the Write Cache and PvD drives the same size.  So I would go with like a 12 or 15GB PvD.

Make sure you read this:

Author Closing Comment

ID: 39810952
Brilliant explanation of the terms Write Cache and PVD.
LVL 37

Expert Comment

by:Carl Webster
ID: 39817469

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

#Citrix #Citrix Netscaler #HTTP Compression #Load Balance
Let’s list some of the technologies that enable smooth teleworking. 
How to install and configure Citrix XenApp 6.5 - Part 1. In this video tutorial we have explained step by step installation of Citrix XenApp 6.5 Server on Windows Server 2008 R2 is explained in this video. We have explained the difference between…
This demo shows you how to set up the containerized NetScaler CPX with NetScaler Management and Analytics System in a non-routable Mesos/Marathon environment for use with Micro-Services applications.

722 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question