> On May 6, 2015, at 6:31 PM, Vladimir Mosgalin <mosga...@vm10124.spb.edu> > wrote: > > Alternative to TRIM-aided GC is Idle Time Garbage Collection (which you > could see on Plextor), which actively scans data in background, finds > empty blocks (zeroes) and marks them as free. Well probably more > complicated than that, but it's the idea.
A quick search indicates that Idle TIme Garbage Collection is just another term for garbage collection. And I don’t see how it can work as well without TRIM as with TRIM, unless massively over provisioned. There is still the issue that, at the file system level, you may now that you just deleted a 1GB file that fully fills a whole lot of EBs. Without trim, the controller can’t know that the blocks aren’t in use until the OS attempts to write to those blocks. if the controller needs to make space, it will have to copy the stale data that it doesn’t know isn’t used anymore. Now, a continous write to a whole EB’s worth of data (still stored in DRAM on the drive), it can see that the whole block can be marked as unused, and freed later. I’m not sure what the zero blocks you are referring to means. If you write a whole bunch of zeros, is it marked as unused? Even if contained in a file? You really can’t mark obsolete data as zeros since you can’t rewrite until you erase first.
