PVs makes storage trembling. Part 5 of this series of blog posts: Summary of new technologies of PVS writing Cache

Summary and parameter recommendations

From the above large number of test results, we can see that the new PVS write cache technology significantly reduces storage read/write, which can eliminate the necessity of purchasing expensive SAN storage, whether you are using xenapp or pooled desktop, it is fully applicable. One of the reasons for this feature of PVS is that it changes the I/O write mode to the disk. A xenapp or a VDI traditionally sends a majority of random write operations in 4 K size to the disk, which is the most difficult size for the hard disk, this is also the main reason why the VDI method puts pressure on San. After cache in RAM with hard disk overflow is configured, All I/O operations are first written to the memory, which is not a problem in the memory. When the memory is full and must overflow to the disk, It will be written into the vhdx file on the disk, and the write is usually written in the unit of 2 MB, data blocks of vhdx files every 2 MB can greatly improve the performance.

Finally, we will give some summary points:

• The PVS write Cache Technology "cache in RAM with hard disk overflow" can indeed reduce the iops per user to less than one iops;

• In future VDI projects, you no longer need to consider purchasing expensive flash disks or SSD hard disks. This can greatly reduce the cost of the VDI project. Now, buy SATA hard disks!

• No matter how much memory you have, all end users who use PVS are advised to upgrade your environment to PVS 7.1 and enable this feature;

• This function uses non-page pool memory (non-paged pool memory), so it is effective only when the memory area is surplus. If the memory of your operating system is too low, you will not be able to allocate any memory space to the write cache. In addition, a good technical feature of this write cache is that this cache type can be used to release unused memory space and hard disk space after files/data blocks in the cache are deleted. In the previous PVS version, once a data block is written to the memory or disk, it will not be released even if it is deleted, this is why you have configured 6 GB for a Windows 7 Virtual Machine on shared storage, and even 8 GB and 10 Gb write cache still takes one week or several weeks to restart. Now, this restart requirement no longer exists. As long as you plan properly, the risk of memory depletion is almost very small;

• For VDI load, even a small amount of memory settings can significantly improve performance. We recommend that you configure a cache of at least 256 MB for a Windows 7 virtual machine, which must be greater than or equal to MB;

  • For Windows 7 of 32bits, MB of cache memory is configured;

  • For Windows 64 bits virtual machines, 3-4 GB of memory is usually required. We recommend allocating MB of memory to the write cache;

  • For Windows 7 64bits virtual machines with over 4 GB of memory, we recommend that you allocate over MB of memory to the write cache;

  • For xenapp-type virtual machines, it is recommended to allocate at least 2 GB space for writing to the cache memory zone. I believe that the memory on the current server is no longer a big problem, therefore, in order to improve performance as much as possible, allocate more than 2 GB of memory space if possible. For example, if your xenapp has allocated 16 GB of memory, we recommend that you allocate at least 4 GB of space to the PVS write cache. Of course, you can test between different values to see which one is the best;

Wish you all the best!

This article is from the Citrix virtual world, you have me blog, please be sure to keep this source http://virtualworld.blog.51cto.com/1412963/1537683