Date: Thu, 25 May 2006 14:11:34 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: anderson@centtech.com Cc: Alexander@Leidinger.net, phk@phk.freebsd.dk, small@freebsd.org, current@freebsd.org Subject: Re: FreeBSD's embedded agenda Message-ID: <20060525.141134.221855237.imp@bsdimp.com> In-Reply-To: <4476036F.4090302@centtech.com> References: <4350.1148583733@critter.freebsd.dk> <4476036F.4090302@centtech.com>
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In message: <4476036F.4090302@centtech.com>
Eric Anderson <anderson@centtech.com> writes:
: 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.
I can help. I don't suffer from the NDA issues that phk has.
Warner
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