Over the last couple of days of Storage Field Day the conversation of Flash vs Cache has been discussed multiple times. Flash vs Cache is an interesting topic for VDI. Do you want to put your whole work load into Flash or use Flash as a Cache and balance the workload with traditional hard drives?
For the purpose of this article I am only listing the vendors that were at Storage Field Day.
Below is list of vendors that are using Pure Flash for their Storage Arrays:
Below is a list of vendors that are using Flash as a Cache
The vendors that are offering a end to end solution with Flash are trying to bring down the cost of Flash by using techniques like duplication, commodity hardware, build your own drives and will talk about power savings. The Flash as Cache camp talk overall cheaper cost per GB, need for cheap disk and that sequential IO are still better on spinning disk.
If you’re after an clear winner for Flash vs Cache it’s just not the simple. The feature sets between all the different vendors vary quit a lot and have different value propositions. I think it’s important to break down what you need for a VDI solution and make your decision based on that.
Replication – You need the ability get user data and golden desktop images offsite and protected. This doesn’t have to fast disk all.
Need for Speed – Your replica’s and linked clones need to be fast. Today’s end users are getting SSD in their laptops. Comparing people’s 5 year old computers to VDI are coming to a close. Your virtual desktop needs to deliver the best performance, consistently.
User Data – profile data, user documents, shortcuts and other users errata. Doesn’t need to be on fast disk unless your making use of redirection. If you’re copying data onto the desktop from a repository you don’t want this to be the bottle neck.
The Trash – Page files, swap files and temp files. They take up lots of space so either you need lots of disk or way to dedupe the data.
Applications – An array providing SMB\CIFS share can go along way for distributing your applications to the desktops. This data\IO will land on the linked clones for the most part but an active non-persistent environment can cause a heavy load on your distribution method of choice.
Over the three days at Storage Field Day I cam really close at changing my stance on which makes the best option. Both Pure Storage and Nimbus have some good products but I still think you need disk. If you where only going to go with one array vendor for VDI I would have to go with Flash as a Cache option. To have only one array vendor in your overall solution can go along way with troubleshooting and managing your environment.
User data is going to continue to grow and I believe more of unstructured, hard to dedupe data will be apart of that make up. Also lots of data will be at rest and never be touched after it’s created, I believe this lends well to a flash as cache scenario. Having the disk in the system also helps for replication if you want to use the standby array for other uses during the day. The replicated data can sit on the disk while other systems can use the flash.
All of the Full SSD vendors of their own unique value proposition like Nimbus with there ultra low cost drives and full feature set of offerings and Pure with their ultra safe no virtual machine never UN-aligned again and dedupe upfront features but I still think you need the spinning rust.