Re: zerofree btrfs support?

[Adam Borowski <kilobyte@angband.pl>]

On Sat, Mar 10, 2018 at 03:55:25AM +0100, Christoph Anton Mitterer wrote:
> Just wondered... was it ever planned (or is there some equivalent) to
> get support for btrfs in zerofree?

Do you want zerofree for thin storage optimization, or for security?

For the former, you can use fstrim; this is enough on any modern SSD; on HDD
you can rig the block device to simulate TRIM by writing zeroes.  I'm sure
one of dm-* can do this, if not -- should be easy to add, there's also
qemu-nbd which allows control over discard, but incurs a performance penalty
compared to playing with the block layer.

For zerofree for security, you'd need defrag (to dislodge partial pinned
extents) first, and do a full balance to avoid data left in metadata nodes
and in blocks beyond file ends (note that zerofree doesn't do this on
traditional filesystems either).


Meow!
-- 
⢀⣴⠾⠻⢶⣦⠀ 
⣾⠁⢠⠒⠀⣿⡁ A dumb species has no way to open a tuna can.
⢿⡄⠘⠷⠚⠋⠀ A smart species invents a can opener.
⠈⠳⣄⠀⠀⠀⠀ A master species delegates.