From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jon Nelson" Subject: Re: Linux RAID Partition Offset 63 cylinders / 30% performance hit? Date: Wed, 19 Dec 2007 11:37:24 -0600 Message-ID: References: <476957A7.5010805@tmr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <476957A7.5010805@tmr.com> Content-Disposition: inline Sender: linux-raid-owner@vger.kernel.org Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 12/19/07, Bill Davidsen wrote: > As other posts have detailed, putting the partition on a 64k aligned > boundary can address the performance problems. However, a poor choice of > chunk size, cache_buffer size, or just random i/o in small sizes can eat > up a lot of the benefit. > > I don't think you need to give up your partitions to get the benefit of > alignment. How might that benefit be realized? Assume I have 3 disks, /dev/sd{b,c,d} all partitioned identically with 4 partitions, and I want to use /dev/sd{b,c,d}3 for a new SW raid. What sequence of steps can I take to ensure that my raid is aligned on a 64K boundary? What effect do the different superblock formats have, if any, in this situation? -- Jon