From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: striping of a 4 drive raid10 Date: Mon, 28 Jan 2008 08:57:18 +1100 Message-ID: <18332.65086.285198.477921@notabene.brown> References: <20080127193345.GA5426@rap.rap.dk> <18332.58858.191866.347099@notabene.brown> <20080127204841.GA10112@rap.rap.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: message from Keld Jorn Simonsen on Sunday January 27 Sender: linux-raid-owner@vger.kernel.org To: Keld =?iso-8859-1?Q?J=F8rn?= Simonsen Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Sunday January 27, keld@dkuug.dk wrote: > On Mon, Jan 28, 2008 at 07:13:30AM +1100, Neil Brown wrote: > > On Sunday January 27, keld@dkuug.dk wrote: > > > Hi > > > > > > I have tried to make a striping raid out of my new 4 x 1 TB > > > SATA-2 disks. I tried raid10,f2 in several ways: > > > > > > 1: md0 = raid10,f2 of sda1+sdb1, md1= raid10,f2 of sdc1+sdd1, md2 = raid0 > > > of md0+md1 > > > > > > 2: md0 = raid0 of sda1+sdb1, md1= raid0 of sdc1+sdd1, md2 = raid01,f2 > > > of md0+md1 > > > > > > 3: md0 = raid10,f2 of sda1+sdb1, md1= raid10,f2 of sdc1+sdd1, chunksize of > > > md0 =md1 =128 KB, md2 = raid0 of md0+md1 chunksize = 256 KB > > > > > > 4: md0 = raid0 of sda1+sdb1, md1= raid0 of sdc1+sdd1, chunksize > > > of md0 = md1 = 128 KB, md2 = raid01,f2 of md0+md1 chunksize = 256 KB > > > > > > 5: md0= raid10,f4 of sda1+sdb1+sdc1+sdd1 > > > > Try > > 6: md0 = raid10,f2 of sda1+sdb1+sdc1+sdd1 > > That I already tried, (and I wrongly stated that I used f4 in stead of > f2). I had two times a thruput of about 300 MB/s but since then I could > not reproduce the behaviour. Are there errors on this that has been > corrected in newer kernels? No, I don't think any performance related changes have been made to raid10 lately. You could try increasing the read-ahead size. For a 4-drive raid10 it defaults to 4 times the read-ahead setting of a single drive, but increasing substantially (e.g. 64 times) seem to increase the speed of "dd" reading a gigabyte. Whether that will actually affect your target workload is a different question. > > > > Also try raid10,o2 with a largeish chunksize (256KB is probably big > > enough). > > I tried that too, but my mdadm did not allow me to use the o flag. > > My kernel is 2.6.12 and mdadm is v1.12.0 - 14 June 2005. > can I upgrade the mdadm alone to a newer version, and then which is > recommendable? You would need a newer kernel and a newer mdadm to get raid10 - offset mode. NeilBrown