Samsung's F2FS filesystem
Posted Oct 8, 2012 19:52 UTC (Mon) by khim
In reply to: Samsung's F2FS filesystem
Parent article: Samsung's F2FS filesystem
What do you mean by FTL ?
Flash translation layer
Does Flash Transition Layer includes wear leveling management for you?
The role of F2FS is not very clear from the announcement. How can you be "Nand Friendly" if you work on a system were the "FTL + wear leveling handling" does everything to hide the Nand ?
FTL is supposed to transparently hide the nature of flash under it. But this layer is extremely leaky. So it makes perfect sense to design filesystem which makes it happier. Well, it's only makes sense in a world where devices with untrunoffable FTS exist, but, for better or for worse, this is exactly how our world is.
Maybe there are some well known limitations to the FTL found in the typical SD card, but I don't know them, so it is not clear to me how F2FS happens to be Nand friendly, when precisely the nand characteristic are carefully hidden by the SD card embedded controller.
It's impossible to hide them. The fact that flash erase block are much higher than write blocks is central feature of flash and it can not be ever fully hidden. Any somewhat sane FTS will handle sequential writes just fine and random writes worse. To the degree that it's speed will drop 10 or 100 times beyond certain threshold. Random reads are fine. These two fundamental, unfixable characteristics are enough to design a filesystem.
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