James Bottomley wrote: > 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. Guilty as charged. Sorry, for some reason I didn't imagine that its parameters would differ from 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 Thank you. I don't want to manhandle that old notebook's fragile vendor proprietary IDE cable again, but I'll try to find another way to test that drive again without going though USB. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
