On 2016-02-09 09:08, Brendan Hide wrote:
On 2/9/2016 1:13 PM, Martin wrote:
How does btrfs compare to f2fs for use on (128GByte) USB memory sticks?
Particularly for wearing out certain storage blocks?
Does btrfs heavily use particular storage blocks that will prematurely
"wear out"?
(That is, could the whole 128GBytes be lost due to one 4kByte block
having been re-written excessively too many times due to a fixed
repeatedly used filesystem block?)
Any other comparisons/thoughts for btrfs vs f2fs?
Copy-on-write (CoW) designs tend naturally to work well with flash
media. F2fs is *specifically* designed to work well with flash, whereas
for btrfs it is a natural consequence of the copy-on-write design. With
both filesystems, if you randomly generate a 1GB file and delete it 1000
times, onto a 1TB flash, you are *very* likely to get exactly one write
to *every* block on the flash (possibly two writes to <1% of the blocks)
rather than, as would be the case with non-CoW filesystems, 1000 writes
to a small chunk of blocks.
This goes double if you're using the 'ssd' mount option on BTRFS. Also,
the only blocks that are rewritten in place on BTRFS (unless you turn
off COW) are the superblocks, but all filesystems rewrite those in-place.
I haven't found much reference or comparison information online wrt wear
leveling - mostly performance benchmarks that don't really address your
request. Personally I will likely never bother with f2fs unless I
somehow end up working on a project requiring relatively small storage
in Flash (as that is what f2fs was designed for).
I would tend to agree, but that's largely because BTRFS is more of a
known entity for me, and certain features (send/receive in particular)
are important enough for my usage that I'm willing to take the
performance hit. IIRC, F2FS was developed for usage in stuff like
Android devices and other compact embedded devices, where the FTL may
not do a good job of wear leveling, so it should work equally well on
USB flash drives (many of the cheap ones have no wear-leveling at all,
and even some of the expensive ones have sub-par wear-leveling compared
to good SSD's).
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