"Ted Ts'o" <tytso@xxxxxxx> writes: > On Mon, Feb 28, 2011 at 04:10:44PM -0500, Jeff Moyer wrote: >> > So it there a reliable way to detect that disk drives that don't have >> > the Read-Modify-Write logic? If that can be reflected up the I/O >> > layer I can have mke2fs enforce that restriction, which currently we >> > only enforce if the logical blocksize is 4k. >> >> That's not enough, I'm afraid. How do you deal with O_DIRECT, for >> example? > > The drives do the read/modify/write, so O_DIRECT works fine from the > OS's perspective. There is some risk of torn pages if you get a crash > at the wrong moment, but that's true whenver you have a misaligned > partition. (At least for the drives that do the RMW in the disk > firmware.) Sorry, I thought we were discussing devices that didn't do read-modify-write: > >> Unlike others drives with Advanced Format, it has not > >> read-modify-write logic, so it can only operate with 4k > >> blocks. Also, mkp noted that the theory of operation was to issue aligned units of 4k, but using 512 byte addressing. So, unless you want to keep a blacklist AND write a remapping layer, I'd say don't buy those drives. Cheers, Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
