On 03/08/2010 10:58 AM, James Bottomley wrote: >> >> On the flipside, though, there really is very little net benefit to 4K >> as opposed to 512 byte logical sectors: the additional protocol overhead >> is relatively minimal, and as long as writes are aligned full blocks, >> there shouldn't be any additional overhead on either the OS or the drive >> side. On the plus side, you get full compatibility with the existing >> software stack. The equation really seems rather simple. > > There's another problem that afflicts 4k drives emulating 512b: they > have to do a read modify write for any isolated 512b write ... that > leads to potential corruption of adjacent 512b blocks if power is lost > at the moment the write is being done. Since most Linux filesystems are > 4k sectors, misalignment really hammers this, plus most journal writes > seem to be done in 512 byte increments. I suppose for USB this could be > regarded as flakey as usual, though. > Misalignment sucks in general. This is nothing new - the RAID and flash people have had these problems for a long time now. It's clear we need to align our filesystems, period. As to the read-modify-write issue: to some degree there is very little you can do about it other than a big enough capacitor. If you can't write a sector atomically and have it stick, you're screwed no matter what. -hpa -- 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
