From mboxrd@z Thu Jan 1 00:00:00 1970 From: Adam Goryachev Subject: Re: Raid10 multi core scaling Date: Tue, 26 Nov 2013 22:19:34 +1100 Message-ID: <529483C6.2080503@websitemanagers.com.au> References: <20131126105859.Horde.-ppIIPYRo99SlH7zGogGx_A@webmail.aeiou.pt> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20131126105859.Horde.-ppIIPYRo99SlH7zGogGx_A@webmail.aeiou.pt> Sender: linux-raid-owner@vger.kernel.org To: Pedro Teixeira , linux-raid@vger.kernel.org List-Id: linux-raid.ids On 26/11/13 21:58, Pedro Teixeira wrote: > I created a Raid10 array with 16 sata 1TB disks and the array > performance > seems to be limited by the md0_raid10 taking 99% of one core and not > scalling to other cores. I tried overclocing the cpu cores and this > lead to > a small increase in performance ( but md0_raid10 keeps eating 99% of one > core ). > > I'm using: > - a phenom X6 at 3600mhz > - 16 seagate SSHDs ( sata3 7200RPM with 8GB ssd cache ) > - 4x marvell 9230 sata3 controllers ( 4 ports each ) pcie 2.0 2x > lanes. > - 8GB ram > - custom 3.12 kernel and mdadm compiled from latest source > > what I did to test performance was to force a check on the array, and > this > leads to mdadm reporting a speed of about 990000K/sec. The hard disks > report a 54% utilization. ( Overclocking the cpu by 200mhz increases the > resync speed a bit and the hdd's utilizartion to about 58% ) > > If I do the same with a raid5 array instead of raid10, them resync > speed > will be almost double of raid10, the harddisk utilization reported > will be > 98-100% and I can see at least two cores being used. AFAIK, the only way to make RAID10 use multiple cores is to actually create 8 RAID1 arrays, and then combine those into a RAID0 linear or RAID0 striped array. Each array will then create a new thread (total of 9 threads) which will then spread across all available cores. There is ongoing work happening to improve this, but I don't think it is available in any released kernel yet. Regards, Adam -- Adam Goryachev Website Managers www.websitemanagers.com.au