From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Kuzminsky Subject: Re: Raid sync observations Date: Tue, 20 Dec 2005 14:33:58 -0700 Message-ID: References: <17320.30528.417691.57401@cse.unsw.edu.au> Return-path: In-reply-to: <17320.30528.417691.57401@cse.unsw.edu.au> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Neil Brown wrote: > You can get better speed on creation with > mdadm -C -l6 -n4 -x2 /dev/sd[ab] missing missing /dev/sd[cd] > > i.e. create with 2 missing devices and 2 spares. Recovery onto the > spares will do purely sequential IO on all devices and so will go > much faster. > Doing this requires regenerating datablocks which is more cpu > intensive that generating P and Q, so there might be some CPU > overhead, but the disk throughput is still much faster. > > In 2.6.16, raid6 resync has been improved somewhat. This will not > affect the initial sync, but resync after a crash will only write > P/Q blocks which are wrong and there are usually very few of those. > This means that it will mostly to sequential reads on all drives, so > you get full device speed. Thanks!! -- Sebastian Kuzminsky