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In-VMware Host Caching – Datrium’s Appliance Specific Host Cache Versus Virtunet’s Host Cache for Any Storage.

In-VMware Host Caching – Datrium’s Appliance Specific Host Cache Versus Virtunet’s Host Cache for Any Storage.

Update as of August 2020 – Datrium has recently been acquired by VMware and as a result, has announced the end-of-life for their DVX product line. Original post follows.

Both Datrium and us differentiate from the rest of the storage appliance vendors in that both of us cache data to cache media in the VMware host instead of the storage appliance, which is the traditional approach.

But the similarities between Datrium’s and our host cache software (called VirtuCache) end there. The top three differences between Datrium DVX DiESL and VirtuCache are:

  1. Our host side caching software accelerates any SAN storage appliance, Datrium’s works only for their own appliance;

  2. We cache writes and reads to in-VMware host cache media, Datrium caches only reads;

  3. We can cache to host RAM and SSD, Datrium can cache to SSD only.

So if you are a Datrium customer and if you are looking to apply the concept of host side caching that you have come to like from Datrium, to your other storage appliances, then you could do so with VirtuCache. We will improve the performance of any SAN based storage appliance, by caching all storage IO (reads and writes) to any in-host SSD (or host RAM).

We believe that caching data to in-VMware host high-speed media (Flash / RAM) is a better option than using Flash/RAM in the storage appliance because the high-speed media in our case is closer to the CPU that consumes ‘hot’ data, and hence the same media performs better in the VMware host than in the appliance. This principle applies equally to both reads and writes and hence we cache both reads and writes to in-host SSD (or RAM). Whereas Datrium decided to cache only reads to ESXi host SSD. The writes in the case of Datrium are cached to their appliance NVRAM, much like a traditional appliance. Datrium founder has these arguments to make in favor of caching writes to the appliance and NOT to in-VMware host cache media, which we disagree with. Our counterpoints to Datrium are on this link.

Also, if you use host RAM with VirtuCache, VirtuCache powered infrastructure will be higher performing than any storage array or hyper-converged appliance because no storage appliance or HCI hardware is capable of using large amounts of RAM in the storage IO path. And RAM is the highest performing storage media there is.

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