Enterprise Computing: So EMC, Where’s Your Thin Persistence?

There’s a way… but it’s not a real “fun” way. If you are a powerpath user, you can use it’s migration enabler to do thick to thin conversions live (at least for Linux & Windows). Here’s where is stops being fun: you present the host new target luns, then you use powermig to sync the source to the target luns. It basically looks for 256k of sequential zeros, and throws those away, if you have a 255k of zero’s and 1k of data it will write everything (the 256k was from memory so it might be off). So for me if I really want to reclaim as much as possible: defrag first (if on windows) then create a large file with nothing but zeros in it, then delete the file so I have the best chance of contiguous zero’s (which is true for any array’s zpr)

This is all done online so I don’t have to do a whole lot of application/customer negotiation for time, but it’s a big pain in the ass if you ask me compared to other vendors of just running it as a low-priority service in the array (but at least the option’s there).

Chris, you are correct SVC 5 brings Zero Impact Zero Detection function to our “Space-efficient” volumes, allowing us to also go from “thick to thin” as well as stay thin by inline detecting zeros.

What is interesting is that 3Par think they need a custom ASIC to do this – when SSE 64bit macros in commodity Intel CPUs provide an almost zero impact mechanism to implement said function.