On Wed, 2012-03-28 at 13:14 +0900, Norman Diamond wrote: > I wrote: > > James Bottomley corrected one of the experts who corrected me yesterday: > >>>> So, the problem is that sd_mod is turning your request for a single block into a request for several blocks. > >> > >> No, it won't be this. Everything below block does exactly what block says. If readahead is the problem, then you need to turn it off in block: > >> echo 0 > /sys/block/<dev>/queue/read_ahead_kb > > > > Thank you. But... > > But it didn't help. Today I put the disk internally in an old notebook, and libata made it /dev/sda. > echo 0 >/sys/block/sda/queue/read_ahead_kb > but sg_dd still insisted on reading an entire page, so it refused to read a good block that was too close to the bad block. This tells me you didn't read the man page on sg_dd. To get it to read a block at a time using SCSI commands, you need sg_dd blk_sgio=1 bs=512 bpt=1 <rest of the arguments> That says use SG_IO and read exactly one block per SCSI command James -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
