Flash disks and FFS layout heuristics

[Alfred Perlstein]

* Poul-Henning Kamp <phk at phk.freebsd.dk> [080331 15:24] wrote:
> In message <20080331222154.C976C5B50 at mail.bitblocks.com>, Bakul Shah writes:
> >On Mon, 31 Mar 2008 13:06:10 PDT Matthew Dillon <dillon at apollo.backplane.com>  wrote:
> >>     But how do you index that information?  You can't simply append the
> >>     information to the NAND unless you also have a way to access it.  So
> >>     does the filesystem have to scan the NAND (or significant portions of it)
> >>     in order to build an index of the filesystem topology in system memory?
> >
> >One possible way:
> >
> >I'd design the system so that each update ends with the write
> >of a root block[1]. 
> 
> This is sort of the approach Margo Seltzer used for her (Kludge-)LFS
> it has many drawbacks, in particular when it comes to recovery.

Can you explain why?

I could see it being a problem because recovering the filesystem's
most recent change might require significant scanning?

-- 
- Alfred Perlstein