On Monday 15 March 2010 06:20, david@xxxxxxx wrote: > >>> For any other partition, pick start cylinder which is a multiple of 8: > >>> > >>> cyl 8*x head 0 sector 1: LBA sector 8*x*255*63 - good (4k aligned) > >>> > >>> This will actually work well for *any* geometry, not only for 63s/255h. > >> > >> Yes, but it does squat for a flash disk that wants, say, 256K alignment. > > > > 4K makes sense. 256K not so much. > > > > 256K alignment is hard to swallow for a lot of reasons anyway. > > Unless the filesystem packs small files into blocks a-la reiserfs, > > 256K block filesystems will be very inefficient for a typical > > storage scenarios. > > the thing is, if the OS can learn that it's more efficiant to write in > 256K aligned chunks, then it can batch up things so that the drive doesn't > have to do a read-modify-write cycle and can instead just replace the > entire chunk. I think Linux already is doing this. The problem is, in many cases OS can't possibly do this, short of using a specially designed filesystem. If you untar a Linux kernel source tarball on a seriously fragmented ext2 filesystem, there will be a lot of discontiguous and/or misaligned writes smaller than 256K. Only smart firmware can help in this case. -- vda -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
