From mboxrd@z Thu Jan 1 00:00:00 1970 From: dong wu Subject: why is md/raid5 sequential write speed so slow? Date: Fri, 8 Jan 2010 13:19:46 +0800 Message-ID: <6c394cc31001072119l2619d8aap627164d34eec6806@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids I have made a test in my server! raid5 capacity:80G, disks:9 IO type IOPS speed(M/s) 1024k seq write 40.67 40.67 512k seq write 70.89 39.45 256k seq write 36.02 34.00 128k seq write 134.19 16.77 64k seq write 232.26 14.52 32k seq write 160.23 5.01 16k seq write 148.48 2.32 8k seq write 151.05 1.18 4k seq write 151.39 0.59 2k seq write 290.90 0.57 1k seq write 526.21 0.51 512B seq write 1076.60 0.53 I don't know why raid5 seq write is so slow. Does delaying write cause this? Best Regards Dong Wu