3 ms·
Where does one find information on erase granularity, and, like, doing the optimizations offered by NVMe ZNS on a "normal" SSD? I assume if you throw a sufficie
by namibj 5y ago
Where does one find information on erase granularity, and, like, doing the optimizations offered by NVMe ZNS on a "normal" SSD?
I assume if you throw a sufficiently uncomplicated ZNS-like workload at them, they don't try to ruin your efforts?
I guess arguably this comes from the lack of availability of ZNS drives, especially ones that aren't outcompeted by a Samsung 980 series drive on workloads that don't exceed the 980's warranty's 600 drive writes over 5 years. And depending on what you're doing, you may even use such drives for the IO-heavy load and retire them after 90% of their TBW to something like fileserver duty.
- wtallis 5y agoFor recent drives, if you're lucky the vendor has implemented the Preferred Write Alignment, Preferred Write Granularity, and corresponding Deallocate alignment and granularity reports, added in NVMe 1.4 (2019). Those values may not exactly correspond to the underlying NAND page and erase block sizes, but can probably be taken at face value for their intended purpose if the drive actually reports values larger than 4kB. Otherwise, finding that kind of low-level NAND specifications often comes down to trawling through TechInsights teardowns and conference proceedings (especially ISSCC, though what gets presented doesn't always match what goes into mass production). A zoned-like workload that is append-only within large chunks and uses a Deallocate (Trim) or Write Zeros command to clear chunks should perform well even on standard SSDs. I don't think the exact zone size has much impact, as long as it's comfortably above the erase block size.