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SubjectRe: io-scheduler tuning for better read/write ratio
Date
Ralf Gross wrote:
> The main problem is with bacula. It reads/writes from/to two
> spoolfiles on the same device.
>
> I get the same behavior with 2 dd processes, one reading from disk, one
> writing to it.
>
> Here's the output from dstat (5 sec intervall).
>
> --dsk/md1--
> _read _writ
> 26M 95M
> 31M 96M
> 20M 85M
> 31M 108M
> 28M 89M
> 24M 95M
> 26M 79M
> 32M 115M
> 50M 74M
> 129M 15k
> 147M 1638B
> 147M 0
> 147M 0
> 113M 0
>
>
> At the end I stopped the dd process that is writing to the device, so you
> can see that the md device is capable of reading with >120 MB/s.
>
> I did this with these two commands.
>
> dd if=/dev/zero of=test bs=1MB
> dd if=/dev/md1 of=/dev/null bs=1M

Try changing /proc/sys/vm/dirty_ratio = 1


Thanks!

--
Al



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