Hello there, and thank you for dropping back for part 3…
I suppose I should start with the disappointing news that I have yet to test this option for VDI in a box. And despite Aaron Parker’s suggestions it wasn’t due to lack of inspiration, it was down to lack of time! This series has gathered allot of interest from both community and storage vendors alike, and I feel I should set the record straight before I got any further:
- This isn’t a production idea, you would be crazy to use this idea in a live environment.
- Throughout this entire project, we’re focusing on pooled stateless. Stateful desktops would be a separate post entirely.
- This wasn’t an attack on products in this market space, merely a fresh view on an old problem.
- If i had the skills or funds necessary to run this project to a production solution, I wouldn’t have posted it. I would already be hard at work creating a reasonably priced product!
Now that my declarations are out of the way, I’d first like to talk about the moral of the story. This isn’t an unfamiliar expression:
IOPS mitigation is not about read IOPS it’s about WRITE IOPS!
VMware, Citrix and Microsoft have similar but very different solutions for read IOPS negotiation. Similar in the sense that they try to negate storage read IOPS. But the key difference with XenServer is the local disk cache via Intellicache has the out of box functionality to cache the majority of read’s to local disk (think SSD*) without the baked in soft limit of 512 MB for Microsoft HyperV and VMware respectively.
Long story short, VMware and Microsoft’s solution is about 512mb of recognizable read IOPS negation un-tuned, but enabled. Of course this value can be tuned upwards, but the low entry point of cache would suggest, at least to me, that tuning up will have an upsetting affect on the host.
This to me is why IntelliCache has the upperhand in the (value add product) VDI space for read IOPS negation and they even throw in the Hypervisor as part of your XenDesktop licensing, so win win, but what about those pesky write IOPS?