The NOVA filesystem

Posted Aug 13, 2017 21:30 UTC (Sun) by giraffedata (guest, #1954)
In reply to: The NOVA filesystem by jem
Parent article: The NOVA filesystem

When you hit the power button, the instruction pointer picks right back up and the machine keeps running.
For that you need not only persistent memory, but also a persistent CPU.

You need persistent a lot more than that. Main memory is only one of myriad holders of state in a computer. Look at how hard suspend/resume is. You can't just store the contents of main memory, power down, then restore that memory upon power up and keep going. Every device in the computer has some volatile memory in it (disk controllers, for example). And since you can't keep the time of day persistent, there is some difficulty there too.

The image I'm getting here is that "persistent memory" is nothing but marketing speak - it's actually just a SSD.
The big conceptual difference is that the CPU can address the memory directly.

This misses Tara_Li's point. This difference affects only what kernel code you write to use it. The user still sees persistent storage that works at solid state speeds, that you could use to store data, which is exactly what SSDs are all about.

But Jon points out one difference between persistent memory and SSD that could actually make a difference in its application: persistent memory is byte-addressable.