Date: Mon, 31 Mar 2008 21:53:47 -0700 From: "Martin Fouts" <mfouts@danger.com> To: "Matthew Dillon" <dillon@apollo.backplane.com> Cc: Christopher Arnold <chris@arnold.se>, arch@freebsd.org, qpadla@gmail.com, freebsd-arch@freebsd.org Subject: RE: Flash disks and FFS layout heuristics Message-ID: <B95CEC1093787C4DB3655EF330984818051D0D@EXCHANGE.danger.com> In-Reply-To: <200803312254.m2VMsPqZ029549@apollo.backplane.com> References: <20080330231544.A96475@localhost> <200803310135.m2V1ZpiN018354@apollo.backplane.com> <B95CEC1093787C4DB3655EF330984818051D03@EXCHANGE.danger.com> <200803312125.29325.qpadla@gmail.com> <200803311915.m2VJFSoR027593@apollo.backplane.com> <B95CEC1093787C4DB3655EF330984818051D09@EXCHANGE.danger.com> <200803312006.m2VK6Aom028133@apollo.backplane.com> <B95CEC1093787C4DB3655EF330984818051D0A@EXCHANGE.danger.com> <200803312254.m2VMsPqZ029549@apollo.backplane.com>
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=20 > -----Original Message----- > From: Matthew Dillon [mailto:dillon@apollo.backplane.com]=20 > Sent: Monday, March 31, 2008 3:54 PM > To: Martin Fouts > Cc: qpadla@gmail.com; freebsd-arch@freebsd.org; Christopher=20 > Arnold; arch@freebsd.org > Subject: RE: Flash disks and FFS layout heuristics > > If I were reimplementing HAMMER as a flash filesystem=20 > (which I am NOT doing), I would probably do away > with the blockmap layer entirely since seek locality of=20 > reference is not needed for a flash filesystem, and the global > B-Tree would serve directly as the named-block topology. Which would lead you almost directly to the sort of performance problems that jffs2 has. Until you've done it, you'll be surprised at the cost of maintaining b-trees in NAND.
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