Articles Tagged with Caching through the Stack

Dell Fluid Cache for SAN


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Back in mid-2011, Dell acquired RNA Networks, a small startup out of Portland, Oregon. At the time Dell purchased it, RNA had a product, MVX, that employed three different ways to pool memory across multiple servers in order to accelerate workloads. One was a way to pool memory as a storage cache in order to speed disk accesses using system RAM. In the spring of 2013, we saw some of these features emerge again as Dell’s Fluid Cache for DAS (direct-attach storage) morphed to use the incredible speed of PCIe-based SSDs instead of RAM. Now, in late 2013 at Dell World, we finally get what many of us have been waiting for: the announcement of the expected availability of Dell Fluid Cache for SAN.

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Caching as a Service

Ask any virtualization administrator what their major pain points are and the first thing on the list will be storage. It isn’t surprising. Storage was likely the first major bottleneck for virtualization, back when it was “the Internet” and not “the cloud.” And as any IT person can tell you, there are two ways storage can be a bottleneck: performance and capacity. Traditionally, the problem of capacity is less complicated to solve than that of performance. To gain capacity you just add disk. To gain performance you needed to select a disk form factor (2.5″ or 3.5″), connection technology (SAS, iSCSI, fibre channel), rotational speed (7200, 10000, 15000 RPM), sometimes a controller (do I get the Dell PERC with 512 MB of cache or 1 GB?), and do the math to figure out how many disks you need to match both the problem of your I/O and its corollary: the problem of your budget. Complicating things, virtualization turned most I/O into random I/O. What might be a nice sequential write from each virtual machine looks pretty random in aggregate. Of course, random I/O is the hardest type of I/O for a disk to do.

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Caching throughout the Stack

One sure way to improve performance is to cache the non-dynamic data of any application. We did this to improve the overall performance of The Virtualization Practice website. However, there are many places within the stack to improve overall performance by caching, and this got me to thinking of all the different types. At the last Austin VMUG, there were at least three vendors selling caching solutions that were designed to improve overall performance by as little as 2x to upwards of 50x improvements. That is quite a lot of improvement in application performance. Where do all these caching products fit into the stack?

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