About That New Cache Type…

As many of you have noticed, PVS 7.1 has a brand new cache type called “Cache in Device RAM with Overflow on Hard Disk.” This new feature of PVS is designed to provide better performance by combining the light speed of RAM with the efficiency of hard disk storage and at the same time avoiding previous hurdles such as unexpected BSOD when using RAM cache due to the memory getting filled up. The new differencing format of the file (VHDX) also resolves the issue when caching to device HD where applications accessing printer drivers would randomly crash.

As some of you have noticed, however, target device performance has not increased dramatically in terms of speed. In fact, some folks out there with IOMeters have reported that IOPs have not improved at all with the new cache type. This is currently a known issue due to a problem turning on the RAM portion of the cache and I know for a fact that Citrix is working on fixing it in the next hotfix release for PVS 7.1. So stay excited!

Edit:

The RAM portion of the this cache type is fixed in CTX140338 which is a target device hotfix.

4 thoughts on “About That New Cache Type…

  1. Hi,

    PVS cache to RAM with overflow. In your opinion is it stable. I’m thinking of using it in a small environment 100 users or so, but don’t want to use a SAN or go out and buy 12 15k drives to accommodate the necessary IO needed. Can I add an extra drive an put the page file, event logs on this drive and use portion for the overflow?

  2. Garry,

    Thanks for your comment. If you want to take full advantage of the new cache type, make sure you apply hotfix PVS710TargetDeviceWX64001 to your targets from http://support.citrix.com/article/CTX139850 which fixes a known issue with the write cache by turning on the RAM portion of it. It is definitely reliable but there is only one caveat to it: the HD part requires more space than the traditional cache on HD due to the way it utilizes data blocks. There is no hard stat on that so it would be useful to do some testing on your end to see how fast it’s filling up (that is only if you ever max out the allocated RAM of course and have to use the spillover functionality). I hope that helps!

  3. Marcelo,

    Thank you for your comment. Cache in device RAM with overflow on hard disk implies your target device has a hard drive which Thin Clients normally do not. The good thing is that you may never need to fail over to HD and use the RAM portion of it as long as you have enough memory resources on the target device (which is individual and relies upon testing) to handle the cache load.

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