On Mon, Feb 01, 2010 at 07:48:01PM -0500, Thor Lancelot Simon wrote: > On Mon, Feb 01, 2010 at 10:59:37PM +0000, Michael van Elst wrote: > > > > It still wouldn't be perfect. Block size is one thing, block alignment > > the next. A filesystem with 1k blocks (filesystem units == clusters) > > has problems to work on disks with 2k blocks (device units == sectors). > > The only solution is expensive buffering and read-modify-write updates. > > Aren't we in fact going to run into this with 512-byte FFS fragments > and disks with 4K sectors?
Yes. FFS with 512-byte fragments and 4K sectors simply does not work. There is no code that handles this and it would be slow anyway. Fragments must be at least as large a disk sector. That already happens almost automatically because of newfs defaults: file system size frag-size < 20 MB 0.5 KB < 1024 MB 1 KB >= 1024 MB 2 KB Maybe there should be another level (1TB?) that choses 4K fragments (and 32KB blocks) by default but newfs will already refuse to create a filesystem with fragments (or blocks) smaller than sectors. And then there is the 64K MAXPHYS limit on the other end. Greetings, -- Michael van Elst Internet: mlel...@serpens.de "A potential Snark may lurk in every tree."