Hi all,
--- Peter Keller <pkeller@globalphasing.com>写道:
> Hi all,
>
> On Wed, 8 Oct 2008, thomas62186218@aol.com wrote:
>
> > Ben,
> >
> > I have seen this same issue as well. I have
> created an md device capable of
> > 425MB/sec using the hdparm -t command, yet an LVM
> volume fully comprising
> > this md device only got about 150MB/sec. I am not
> sure what the issue is. I
> > am running Ubuntu Hardy 804 server edition,
> 64-bit.
> >
> > -Thomas
>
> I have fixed this kind of problem by tweaking the
> readahead of the LVM
> volume using 'blockdev --setra' and/or 'blockdev
> --setfra'.
It make effect
blockdev --setra 65536 /dev/md0
blockdev --setra 65536 /dev/mapper/DG5-lv1
dd if=/dev/md0 of=/dev/null bs=1M
353185562624 bytes (353 GB) copied, 420.033 s, 841
MB/s
dd if=/dev/mapper/DG5-lv1 of=/dev/null bs=1M
155551006720 bytes (156 GB) copied, 216.576 s, 718
MB/s
Warm regards,
-Ben
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