From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sevrin Robstad Subject: Re: bad performance on RAID 5 Date: Thu, 18 Jan 2007 21:43:12 +0100 Message-ID: <45AFDBE0.9090507@start.no> References: <45AE9640.1040500@start.no> <45AFBC85.8020500@maine.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7BIT Return-path: In-reply-to: <45AFBC85.8020500@maine.edu> Sender: linux-raid-owner@vger.kernel.org To: Steve Cousins Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Steve Cousins wrote: > Sevrin Robstad wrote: >> I'm suffering from bad performance on my RAID5. >> >> a "echo check >/sys/block/md0/md/sync_action" >> >> gives a speed at only about 5000K/sec , and HIGH load average : > What do you get when you try something like: > > time dd if=/dev/zero of=/mount-point/test.dat bs=1024k count=1024 > > where /mount-point is where /dev/md0 is mounted. > > This will create a 1 GiB file and it will tell you how long it takes > to create it. Also, I'd try running Bonnie++ on it to see what the > different performance values are. > > I don't know a lot about the md sync process but I remember having my > sync action stuck at a low value at one point and it didn't have > anything to do with the performance of the RAID array in general. > I ran the a couple of times, and got either about 28MB/s or about 34MB/s. strange. When I run the same test on a single disk connected to another controller I get about 60MB/s. [root@compaq ~]# time dd if=/dev/zero of=/mnt/gigaraid/1gb.testfile bs=1024k cou nt=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 38.1873 seconds, 28.1 MB/s real 0m38.321s user 0m0.009s sys 0m8.602s [root@compaq ~]# time dd if=/dev/zero of=/mnt/gigaraid/1gb.testfile bs=1024k cou nt=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 31.4377 seconds, 34.2 MB/s real 0m31.949s user 0m0.016s sys 0m8.988s [root@compaq ~]# time dd if=/dev/zero of=/mnt/gigaraid/1gb.testfile bs=1024k cou nt=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 37.599 seconds, 28.6 MB/s real 0m38.151s user 0m0.011s sys 0m9.291s [root@compaq ~]# time dd if=/dev/zero of=/mnt/gigaraid/1gb.testfile bs=1024k count=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 31.2569 seconds, 34.4 MB/s real 0m31.765s user 0m0.007s sys 0m8.913s [root@compaq ~]# time dd if=/dev/zero of=/mnt/gigaraid/1gb.testfile bs=1024k count=1024 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 37.4778 seconds, 28.7 MB/s real 0m37.923s user 0m0.009s sys 0m9.231s