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SubjectRe: O_DIRECT to md raid 6 is slow
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 <kedacomkernel@gmail.com> wrote:
> On 2012-08-15 08:49 Andy Lutomirski <luto@amacapital.net> Wrote:
>>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?
>
>>--Andy
>>
>>--
>>Andy Lutomirski
>>AMA Capital Management, LLC
>>--
>>To unsubscribe from this list: send the line "unsubscribe linux-raid" in
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--
Andy Lutomirski
AMA Capital Management, LLC


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