I recently wrote about the new Datrium 3.0 release with blogs here and here, including the support for Red Hat Virtualization and mind-boggling performance numbers. However, during my writing, I forgot to include a new and critical feature that adds enhanced resiliency to the platform and protect the applications even is the last local flash device fails.
Peer Cache Mode
In DVX, we hold all data in use on flash on the host. Moreover, we guide customers to size host flash to hold all data for the VMDKs. With always-on dedupe/compression for host flash as well, this is feasible – with just 2TB flash on each host and 3X-5X data reduction you can have 6-10TB of effective flash. (DVX supports up to 16TB of raw flash on each host). Experience proves this is in fact what our customers do: by and large, our customers configure sufficient flash on the host and get close to 100% hit rate on the host flash.
However, in most instances due to data reduction benefits, customer decide to have only 1 or 2 flash devices on each server, because that’s more than enough from a capacity and performance standpoints. With previous releases of DVX if the last available flash device failed the workload would then stop, and applications would have to be restarted, manually or via HA, on a different host.
With DVX 3.0 we are introducing the ability to utilize Peer Cache, the flash devices from other hosts, to keep the workload running even if the last available flash device fails, and without drastically impacting application performance until new flash devices are placed. As with any array, you now would have to traverse the network, and there would be some additional latency, but in this case, DVX would be working like any other SAN.
As with any array, you now would have to traverse the network for IO read operations, and there would be some additional latency given that we would be introducing East <-> West traffic for reads instead of being local. But in this case, DVX would be working just like a SAN.
This article was first published by Andre Leibovici (@andreleibovici) at myvirtualcloud.net.