Date: Mon, 31 Mar 2008 15:29:38 -0700 From: Alfred Perlstein <alfred@freebsd.org> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: Christopher Arnold <chris@arnold.se>, Martin Fouts <mfouts@danger.com>, arch@freebsd.org, qpadla@gmail.com, freebsd-arch@freebsd.org Subject: Re: Flash disks and FFS layout heuristics Message-ID: <20080331222938.GS95731@elvis.mu.org> In-Reply-To: <26080.1207002217@critter.freebsd.dk> References: <20080331222154.C976C5B50@mail.bitblocks.com> <26080.1207002217@critter.freebsd.dk>
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* Poul-Henning Kamp <phk@phk.freebsd.dk> [080331 15:24] wrote: > In message <20080331222154.C976C5B50@mail.bitblocks.com>, Bakul Shah writes: > >On Mon, 31 Mar 2008 13:06:10 PDT Matthew Dillon <dillon@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
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