One of the sticky wickets that holds back thin provisioning is the need to communicate when capacity is no longer needed. Enterprise storage arrays can reclaim zeroed pages, but writing all those zeros can really fill up an I/O queue. This is where WRITE_SAME comes into the picture. This is a really terrible name. It's all-capital letters and has an underscore in the … [Read more...] about What is WRITE_SAME? Green Eggs and Ham!
zero page reclaim
In the previous post, I talked about how the Drobo uses metadata monitoring to solve the telephone game and make de-allocation possible. But that approach is challenging in complex enterprise environments. Instead, most enterprise arrays use a complex chain of semaphores to interpret signals from the connected hosts about the capacity that can be un-provisioned. On the … [Read more...] about Zero Page Reclaim: Savior of Thin Provisioning?