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Message-ID: <Pine.LNX.4.64.0706181113050.12717@asgard.lang.hm> Date: Mon, 18 Jun 2007 11:16:32 -0700 (PDT) From: david@...g.hm To: Brendan Conoboy <blc@...hat.com> cc: Neil Brown <neilb@...e.de>, Wakko Warner <wakko@...mx.eu.org>, linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org Subject: Re: limits on raid On Mon, 18 Jun 2007, Brendan Conoboy wrote: > david@...g.hm wrote: >> I plan to test the different configurations. >> >> however, if I was saturating the bus with the reconstruct how can I fire >> off a dd if=/dev/zero of=/mnt/test and get ~45M/sec whild only slowing the >> reconstruct to ~4M/sec? >> >> I'm putting 10x as much data through the bus at that point, it would seem >> to proove that it's not the bus that's saturated. > > I am unconvinced. If you take ~1MB/s for each active drive, add in SCSI > overhead, 45M/sec seems reasonable. Have you look at a running iostat while > all this is going on? Try it out- add up the kb/s from each drive and see > how close you are to your maximum theoretical IO. I didn't try iostat, I did look at vmstat, and there the numbers look even worse, the bo column is ~500 for the resync by itself, but with the DD it's ~50,000. when I get access to the box again I'll try iostat to get more details > Also, how's your CPU utilization? ~30% of one cpu for the raid 6 thread, ~5% of one cpu for the resync thread David Lang - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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