Design and deployment of PVS write cache capacity

Tip: This article was an e-mail I wrote in November 5, 2011, because the content will be referenced in a new blog to be published, so I will re-post it here. Because of the content of the past three years, technology is constantly improving. Some of the content is no longer suitable for the present and only for understanding the development of technology.

Citrix blogs often have some in-depth blogs, which are suitable for masters. Some blogs are also good at induction and suitable for experience summarization. Today, I saw a blog post about the latter. I will explain the Capacity Design and deployment of PVS write cache for your reference.

The author of PVS writecache sizing & considerations made a questionnaire survey after writing an article. The author actually investigates how PVS users configure write cache: pvswrite cache sizing & considerations-Follow up

 

We Abstract The Essentials of some of the first blogs:

I. Deployment location

1. You can deploy the write cache

• Cache on provisioningserver

• Cache on target device Ram

• Cache on target device harddrive

1. Set the write cache to target side.

   Benefits

   1. It keeps the write "close" to the target;

   2. Minimizes the load on theprovisioning servers

   3. This disk can also be usedfor data, which needs to be persistent

Disadvantages

1. 1. It requires more resourceson the target side

       

2. Author's tendency:

   Personally I prefer using a target side hard disk for storingthe write cache for virtual hosted tops and xenapps.

 

Ii. Local Disks

1. Advantages and disadvantages of writing cache deployment for Ephemeral disks and shared storage:

Option 1-write cache disk on sharedstorage

Pro:

• High level of performance (typically)

• Easy to scale

• Central monitoring andmanagement

• Virtual targets can bemoved between hypervisor hosts for load balancing and/or management reasons

  Con:

• Complexity

• Cost

• Available disk space onhypervisor hosts is wasted

   

  Option 2-write cache disk on localdisk

  Pro:

• Cheap (compared to sharedstorage)

• Low Complexity

  Con:

• Can be a performancebottleneck/hard to scale

• Virtual targets are "tied" to a hypervisor host

• Hypervisor hosts must havelocal drives

   

  There is no such sword to tell you which one is the best, and the actual choices of users are different.

   

1. Author's Point of View

Personally I prefer to use local disks for provisioned xenappservers whenever possible from an performance and management point of view.

The hard disk on the blade is not suitable, because the blade usually has only two hard disks, which cannot meet the concurrent needs of the virtual desktop.

 

Iii. Disk size

1. It is impossible to estimate the size of the write cache, because it depends largely on the user's behavior and the working mode of the application.

   1. For example, you can copy a large number of files to the write cache;

   2. Applications cache a large number of files, such as database files;

2. Theoretically, the write cache cannot exceed the vdisk size. Of course, this will not happen in 99.99999% cases;

3. How to Reduce the write cache size and improve read/write Efficiency

   1. Folder Redirection: Keep the user profile small by redirecting profile folders suchas desktop, my documents, application data and so on.

   2. Use the app-V shared cache or the latest citrixapplication streaming. The latter now has a vhd Mount feature (similarto app-V shared cache) and does not build a streaming cache locally.

4. Files permanently saved on the local hard disk after the device is restarted

   1. Windows pagefile ..

   2. Windows event log.

   3. Citrix related logs.

   4. Anti-virus pattern.

   5. App-V/Application streaming cache in case a shared cacheconcept cannot be used.

   6. EdgeSight dB.

       

      4. Local Disks

      After redirecting the write cache and other items to the target's local permanent disk, we need to consider two things:

5. Permanent

   1. Remember that writing files on a permanent disk violates the original intention of central PVS management. We need to consider how to manage or delete these files;

   2. The size of the disk drive. If the capacity of the local disk is insufficient to support the write cache, if not, the write cache will be written to the PVS server.

6. Example

Assume that there is a xenapp server with 50 concurrent users, each user has a 20 m user profile, and each user has created a 50 m working environment (such as a temporary file). The calculation result is as follows:

1.0 GB user profiles (50x20 MB)

2.5 GB user workspace (50x50 MB)

1.0 GB system workspace (assumed, different for everyenvironment)

 

= 4.5 GB write cache file

 

4.5 GB write cache file

4.0 GB pagefile (check out kb889654/kb2021748)

0.1 GB windows Event Logs

0.1 GB Citrix logs

0.3 GB EdgeSight

1.0 GB other

4.0 GB dedicated dump file (see update section below)

2.0 GB buffer (some room to grow)

 

= 16 GB local disk size required per xenapp target

 

V. Survey results

 

1.0 GB other

4.0 GB dedicated dump file (see update section below)

2.0 GB buffer (some room to grow)

 

= 16 GB local disk size required per xenapp target

 

V. Survey results

 

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Design and deployment of PVS write cache capacity