Messages in this thread | | | Subject | Re: [PATCH 00/22 take 3] UBI: Unsorted Block Images | From | Thomas Gleixner <> | Date | Wed, 21 Mar 2007 12:25:34 +0100 |
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On Wed, 2007-03-21 at 12:05 +0100, Jörn Engel wrote: > On Tue, 20 March 2007 01:42:46 +0100, Thomas Gleixner wrote: > > On Mon, 2007-03-19 at 17:32 -0500, Matt Mackall wrote: > > > > > > > 4. JFFS2 has its own wear-leving scheme, as do several other > > > > > filesystems, so they probably want to bypass this piece of the stack. > > > > > > > > JFFS2 on top of UBI delegates the wear levelling to UBI, as JFFS2s own > > > > wear levelling sucks. > > > > > > Ok, fine. How about LogFS, then? > > > > LogFS can easily leverage UBI's wear algorithm. > > Ok, now we have reached the absurd. UBI quite fundamentally cannot do > wear leveling as good as LogFS can. Simply because UBI has zero > knowledge of the _contents_ of its blocks. Knowing whether a block is > 90% garbage or not makes a great difference. > > Also LogFS currently requires erasesizes of 2^n.
Last time I talked to you about that, you said it would be possible and fixable. We talked about several mechanisms, which would allow a filesystem or other users to hint such things to UBI.
Even if the LogFS wear levelling is so superior, it CAN'T do across device wear levelling.
tglx
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