From linux-kernel Sun Dec 26 22:07:45 2010 From: Niels Date: Sun, 26 Dec 2010 22:07:45 +0000 To: linux-kernel Subject: Re: Slow disks. Message-Id: X-MARC-Message: https://marc.info/?l=linux-kernel&m=129340129128798 On Friday 24 December 2010 16:24, Michael Tokarev wrote: [snip] > The thing is, for these WD*EARS drivers, it is _vital_ to get > proper alignment of all partitions and operations. They've > 4Kb sectors physically but report 512bytes sectors to the OS. > It is _essential_ to ensure all partitions are aligned to the > 4Kb sectors. Be it LVM, raid-something, etc - each filesystem > must start at a 4kb boundary at least, or else you'll see > _dramatic_ write speed problems. > > So.. check the whole storage stack and ensure proper alignment > everywhere. In particular, check that your partitions are not > aligned to 63 sectors (512b), or starts at N+1 sector - the > most problematic mode for these drives. [snip] I have several of these drives, in various sizes. They seem to be aligned to 63 as you mention: Device Boot Start End Blocks Id System /dev/sda1 63 208844 104391 83 Linux /dev/sda2 208845 19759949 9775552+ 82 Linux swap / Solaris /dev/sda3 19759950 215094284 97667167+ 83 Linux /dev/sda4 215094285 781417664 283161690 83 Linux Device Boot Start End Blocks Id System /dev/sdb1 63 1953520064 976760001 83 Linux Is that bad? What can I do to repair it? What can I do to prevent it from happening again? Thanks, Niels -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/