Cache – The Datrium DVX Worst Case is Someone Else’s Best Case
A couple of times I have been asked about caching performance with Datrium DVX. It’s intuitive for people without an understanding of the technology to think that DVX performance is contingent entirely on the host cache and if nodes go down the caches would have to be rewarmed, or a full cache integrity checks would be necessary, like in ZFS with L2ARC. In the L2ARC case, performance could drag for hours until the cache is repopulated.
That is not the case with DVX…
In DVX, we hold 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 capacity. (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.
With any array, you have to traverse the network. However, with any modern SSD, the network latency can be an order of magnitude higher than the device access latency. Flash does belong in the host, especially if you are talking about NVMe drives with sub-50usec latency.
Read the entire article here, Cache – The Datrium DVX Worst Case is Someone Else’s Best Case – myvirtualcloud.net
via Andre Leibovici at myvirtualcloud.net