Date: Mon, 29 May 2006 10:49:28 -0700 From: "marty fouts" <mf.danger@gmail.com> To: "James Mansion" <james@wgold.demon.co.uk> Cc: Alexander Leidinger <Alexander@leidinger.net>, Poul-Henning Kamp <phk@phk.freebsd.dk>, Andrew Atrens <atrens@nortel.com>, small@freebsd.org Subject: Re: FreeBSD's embedded agenda Message-ID: <9f7850090605291049j2d6c6e41wff1330e114fa91a7@mail.gmail.com> In-Reply-To: <HCEPKPMCAJLDGJIBCLGHEEILFGAA.james@wgold.demon.co.uk> References: <9f7850090605271000j524d6a35gfa3f6df1f0ed59f5@mail.gmail.com> <HCEPKPMCAJLDGJIBCLGHEEILFGAA.james@wgold.demon.co.uk>
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On 5/28/06, James Mansion <james@wgold.demon.co.uk> wrote: > >Experience suggests that wear leveling does matter in this market, but > >that fairly simple wear leveling can be very effective. > > Can I ask why? I mmay be a very bed person to talk about phones, > because I have a 6-year-old Seimens I chose for battery life and > the first thing I did was disable IrDa and WAP. It doesn't have > a camera. ;-) And I've never sent a text. > Two reasons: First, NAND devices have a complicated wear behavior. The more frequently you hit the same block, the lower the life expectancy of the block. Second, Because of the way NAND storage is used in smartphones, One tends to accumulate fairly full devices, so the handful of data that is frequently written tends to be limited to a small part of the system. Many blocks see very little wear while a few blocks see a lot of wear. This is exacerbated by the block size being large. (smartphones tend to use NAND rather than NOR because of the cost difference) Because of the relatively large block size, you have to do garbage collection anyway, and it's not hard to do modest wear leveling while you're doing that.
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