3 ms·
additionally SSDs use garbage collection algorithms so are fraught with the possibility of a write taking an unbounded amount of time, even if nothing is malfun
by throwaway2048 7y ago
additionally SSDs use garbage collection algorithms so are fraught with the possibility of a write taking an unbounded amount of time, even if nothing is malfunctioning, which is pretty scary.
To head off replies about fixed time garbage collection, sure it exists, but you cant guarantee it will reclaim enough space in a fixed timeslot (think of a massively pathological case where 99% of every flash chip is full, but super fragmented and data needs to be shuffled around perhaps hundreds or even thousands of times before enough space can be reclaimed)
- Dylan16807 7y ago> To head off replies about fixed time garbage collection, sure it exists, but you cant guarantee it will reclaim enough space in a fixed timeslot (think of a massively pathological case where 99% of every flash chip is full, but super fragmented and data needs to be shuffled around perhaps hundreds or even thousands of times before enough space can be reclaimed) That's why you have spare space. It's not overly hard to clamp write amplification to a number like 10x or 20x, even in the absolute worst case. Note that the SD standard here requires a minimum number of writes per second inside a 256MB area, and even 1% spare space on a 32GB card would give you a >256MB buffer.