Re: Snapshots in tmpfs

[David Holland <dholland-tech%netbsd.org@localhost>]

On Thu, Feb 23, 2012 at 08:04:01PM -0500, Thor Lancelot Simon wrote:
 > > > > > Is CHFS really suitable for CompactFlash?  Is LFS even usable?
 > > > > 
 > > > > No 
 > > > 
 > > > I thought the whole point of chfs was to be able to operate on raw
 > > > flash devices that don't have their own flash translation layer.
 > > 
 > > Oh, my mistake, since there was concern about filesystem type I
 > > thought you were talking about raw flash, but apparently CompactFlash
 > > is not raw flash, same as USB sticks aren't.
 > > 
 > > In that case, just use wapbl.
 > 
 > That doubles the write rate for the common "create new version of
 > file and rename into place" pattern...

Uh no, no it doesn't, it doesn't even approximate it unless you're
continuously writing new versions of lots of files.

Furthermore, remember, it does so in order to give some chance that a
crash or power failure won't wipe out the data. Ad hoc workarounds
(including this tmpfs snapshots scheme) will lose that property.

(Also, doubles relative to what? Remember that these devices are
designed with FAT32 in mind.)

-- 
David A. Holland
dholland%netbsd.org@localhost