[Btrfs-devel] btrfs and Solid State Disks (SSD).

[Miguel Figueiredo Mascarenhas Sousa Filipe]

Hi to All,

On Feb 11, 2008 8:34 PM, Claudio Martins <ctpm at ist.utl.pt> wrote:
> On Monday 11 February 2008, Miguel Figueiredo Mascarenhas Sousa Filipe wrote:
> >
> > >From what I read, current SSD are characterized by:
> >
> > - poor performance in random writes (because of block erasure)
> > - require wear leveling, even those that emulate sata/ide/scsi disk
> > with onboard wear leveling logic.
>
>  I thought that SSDs that emulate scsi disks (like USB pen drives, etc) and
> also CompactFlash and SD cards, had no need of additional wear leveling since
> they have, as you say, onboard wear leveling logic because they were
> basically designed to work well with FAT16/32.
> Though I'd also really like to hear if anyone on the list has more information
> about this problem.

I've read this from the author of LogFS (Joern Engel).
In this post http://linux.derkeiler.com/Mailing-Lists/Kernel/2007-06/msg05668.html
he mentions that wear leveling is done by splitting the device in
zones (about 1024 blocks each zone)
and that all wear leveling is done inside of that zone. This happens
of course on all zones.
That works fine for FAT, since the ondisk layout of it is quite
widespread, not that well on ext family of filesystems.

That post is also a good read for learning bit more about the
internals of nowadays "pendrives".

Kind regards,

-- 
Miguel Sousa Filipe