From mboxrd@z Thu Jan 1 00:00:00 1970 From: thomas62186218@aol.com Subject: Software RAID 6 initial sync very slow Date: Sun, 01 Jun 2008 07:26:58 -0400 Message-ID: <8CA91F18992AC9E-1724-EAF@webmail-ne13.sysops.aol.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; 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 all, I am debating between hardware or software RAID for a high-performance Linux storage server. One area of concern in my initial mdadm tests concerns sync speed. My setup is as follows: Linux Fedora 7 x64 12 x 1TB Hitachi 1TB SATAII drives connected via LSI SAS3801E PCIe HBA Dual 2.5GHz quad-core Xeon 8GB RAM My first test was to create a RAID 6 md device, 128K chunk, with all 12 drives. The sync is currently underway at a very slow 30MB/sec, with mdadm estimating this as a 9hr process. With an Adaptec 5805 RAID card tested, I performed the RAID 6 initial sync with the same 12 drives in just under 5 hours. Meanwhile, our total CPU usage during mdadm syncing is at 5%, so there's plenty of CPU not being used. Why is the sync so slow? This concerns me not only because initial sync time is important, but because this may be indicative of slow sync times in the event of a drive failure. Thanks for your input, Thomas