Date: Thu, 25 May 2006 14:20:15 -0500 From: Eric Anderson <anderson@centtech.com> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: Alexander Leidinger <Alexander@Leidinger.net>, small@freebsd.org, current@freebsd.org Subject: Re: FreeBSD's embedded agenda Message-ID: <4476036F.4090302@centtech.com> In-Reply-To: <4350.1148583733@critter.freebsd.dk> References: <4350.1148583733@critter.freebsd.dk>
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Poul-Henning Kamp wrote: > In message <4475EFC1.1020504@nortel.com>, "Andrew Atrens" writes: > >>>> Said kernel would have a low level driver that makes plain >>>> old flash chips look (and behave) like a disk. It would support >>>> wear-levelling, [...] >>>> >>>> Then you could throw FFS on top of that. >>> This is exactly what you do not want to do. >>> >>> You want to write a flash friendly filesystem which knows what >>> a flash is, and which does the wear levelling internally. >>> >>> The reason Flash Adaptation Layers came about in the first place >>> is that W95 didn't support anything but FAT. >> Hmm. I was thinking about partitioning the problem actually. Make flash >> look like a disk and then you can put any filesystem on it that you >> want. Seems a heck of a lot simpler .. and I'm not sure if I see any >> drawbacks to doing it that way ... > > The main one is that the flash adaptation layer does not have the > full information to work with for deciding wear-leveling decisions > and the filesystem has no idea what the optimal block allocation > strategy is for the flash device. > > Flash devices have no seek time penalty, and therefore the block > allocation should focus on wear-leveling rather than seek time > optimization. > This sounds like an awefuly fun project to me. Is anyone (PHK?) willing to help me with some of the FreeBSD kernel related issues? If so, I'd like to work on this. Eric -- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology Anything that works is better than anything that doesn't. ------------------------------------------------------------------------
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