Re: O_DIRECT to md raid 6 is slow
From: Andy Lutomirski <luto@amacapital.net>
Date: 2012-08-15 01:12:48
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Ubuntu's 3.2.0-27-generic. I can test on a newer kernel tomorrow. --Andy On Tue, Aug 14, 2012 at 6:07 PM, kedacomkernel [off-list ref] wrote:
On 2012-08-15 08:49 Andy Lutomirski [off-list ref] Wrote:quoted
If I do: # dd if=/dev/zero of=/dev/md0p1 bs=8M then iostat -m 5 says: avg-cpu: %user %nice %system %iowait %steal %idle 0.00 0.00 26.88 35.27 0.00 37.85 Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn sdb 265.20 1.16 54.79 5 273 sdc 266.20 1.47 54.73 7 273 sdd 264.20 1.38 54.54 6 272 sdf 286.00 1.84 54.74 9 273 sde 266.60 1.04 54.75 5 273 sdg 265.00 1.02 54.74 5 273 md0 55808.00 0.00 218.00 0 1090 If I do: # dd if=/dev/zero of=/dev/md0p1 bs=8M oflag=direct then iostat -m 5 says: avg-cpu: %user %nice %system %iowait %steal %idle 0.00 0.00 11.70 12.94 0.00 75.36 Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn sdb 831.00 8.58 30.42 42 152 sdc 832.80 8.05 29.99 40 149 sdd 832.00 9.10 29.78 45 148 sdf 838.40 9.11 29.72 45 148 sde 828.80 7.91 29.79 39 148 sdg 850.80 8.00 30.18 40 150 md0 1012.60 0.00 101.27 0 506 It looks like md isn't recognizing that I'm writing whole stripes when I'm in O_DIRECT mode.kernel version?quoted
--Andy -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
-- Andy Lutomirski AMA Capital Management, LLC