Comment by rowanG077
4 years ago
I think most SSD have dram cache on board. Could they design issue here be Apple doesn't have that and instead using system RAM as SSD dram cache?
4 years ago
I think most SSD have dram cache on board. Could they design issue here be Apple doesn't have that and instead using system RAM as SSD dram cache?
They do use system RAM as cache, but that has no effect on performance. If anything it should be way faster than the puny RAM cache chips on typical SSDs. It doesn't explain the slow flush perf.
Afaik if you fsync an SSD with dram cache it won't hit the NAND cells. Those SSD do have some way to flush before they lose juice though.
This was for enterprise SSD though a few years back.
That is only for enterprise SSDs. Consumer SSDs do not have capacitor banks to do a full DRAM flush. Some have capacitor banks to ensure data at rest integrity and some use another mechanism for that, but I'm not aware of any that will guarantee full cache stability.