What is Intel Optane DC Persistent Memory in simple words ?
This will be my first post from a series of posts I intend to write about Intel Optane DC Persistent Memory (PMEM) and I am going to start with some very simple concepts, so that the technology can be well understood.
Intel Optane DC Persistent Memory is a new technology released by Intel in 2019.
It resembles to a DRAM DIMM, can be fitted to a DRAM slot, but works very differently than a traditional DRAM DIMM. It comes with various sizes ranging from 128/256/512GB and even more in the future.
We can say that Intel Optane DC Persistent Memory has a dual personality, known as “APP Direct Mode” and “Memory Mode”. I will explain later how to change the personalities but for now we are only to focus at a high level about these 2 operations mode.
In APP Direct Mode, PMEM can be used as a permanent storage device that can be consumed by any VMs (if you are using virtualization) or by the Guest OS that runs on the server. The advantage of that mode is that it provides tremendous performance at an incredible low latency. By tremendous I mean something ranging between 1-2 Million IOPS for 4KB Random Reads on a single PMEM cards at a latency under 20 microseconds (0.002 ms).
In Memory Mode, PMEM is used as the system main memory but on a partnership with the server local DRAM! This means that under the covers the Guest OS or Hypervisor will only see the total PMEM size as the main system memory, but the DRAM will be used in the background as “Near Memory” and PMEM will be considered “Far Memory”. If you are familiar with VMware VSAN, it’s pretty much like the same concept as a VSAN Disk Group. The DRAM will be used to serve most of the Memory requests whenever possible and if the data cannot be kept within the DRAM region it will be served by PMEM at a higher latency cost. This mode has the advantage of reducing costs (PMEM is significantly cheaper than DRAM) and also achieve higher consolidation ratios without compromising the performance if the system is sized correctly (we need to have a good balance of DRAM and PMEM).
virtualvmx 