From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: RAID-6 question. Date: Mon, 17 Nov 2008 08:09:50 -0800 Message-ID: <4921974E.8050508@zytor.com> References: <4920BB05.3050206@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Justin Piszcz Cc: Linux-Raid List-Id: linux-raid.ids Justin Piszcz wrote: > > Yeah, one core was pegged at 100% for the resync, another (md_raidX) > process > was at ~35% on the second core. The third and fourth core were unused > but immediately when I start the resync it definitley slowed down the > system quite a bit and hurt interactivity and as I mentioned before > *without* specifying a lower rebuild speed than the system's maximum I/O > the system is unusable until the rebuild completes, perhaps its a > combination of using all of the one core for the resync where raid5 may > not? I recall w/raid5 I did not have to specify a lower limit for > max_rebuild KiB/s.. > RAID-5 recovery can use the normal accelerated functions, whereas RAID-6 recovery can't (only a handful of CPUs have the operations needed to accelerate dual-disk recovery, and even for those it is not implemented at this point.) -hpa