From mboxrd@z Thu Jan 1 00:00:00 1970 From: Manish Awasthi Subject: md raid performance with 3-18-rc3 Date: Mon, 24 Nov 2014 13:40:06 +0530 Message-ID: <5472E7DE.5070702@caviumnetworks.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi, We benchmarked the md raid driver performance on 3-18-rc3 kernel and compared the results with that of 3.6.11. The reason for this exercise is to understand if multithreaded raid driver has any performance benefits over 3.6.11 which is single threaded. Here are some details about the setup System: Intel(R) Xeon(R) CPU E3-1230 V2 @ 3.30GHz 4 cores (8threads), 8GB RAM. Setup: 3 SSDs create a raid5 array test tool: iozone (only read/re-read, write/re-write tested), blocksize: 4k-64k, filesize: 1Gig to 200Gig Comparison was done for speed of data transfer in kBytes/sec and also the CPU utilization as reported by iozone. raid on 3.18.0-rc3 performed much worse than raid on 3.6.11. Read/Write: raid on 3.18.0-rc3 operated at almost half the speed of raid on 3.6.11 CPU Utilization: With md raid on 3.18.0-rc3, the CPU utilization was less than half of md raid on 3.6.11 on WRITE operations. However, for READ operations, 3.18-0.rc3 had more CPU utilization than 3.6.11. Also, I noticed that scaling up the CPU cores of the system scales down the raid througput with 3.18.0-rc3. I do have detailed logs of the comparison but I'm not sure I should send those on this mailing list. If my observation aligns with someone else's, then what is really the gain with multithreaded raid. Manish