Re: Wheezy regressions on QNAP TS-419P+: port issue?
On Tue, Sep 27, 2011 at 8:24 AM, Jari Kirma <jari@kirma.fi> wrote:
> I recently installed Debian Squeeze on a new TS-419P+, and it ran
> nicely. So, to make it more interesting, I upgraded to Wheeze, and now
> I'm seeing a performance/responsiveness regression whose cause I can't
> quite figure out.
>
> This has following symptoms:
>
> - Big-file dd with large block size (over 16 kiB or so, but especially
> like 1 MiB), from both RAID-5 backed files and bare disks performs
> much slower (30-60%!) than before.
> - dd with small blocks (4 kiB would seem to be close to sweet spot)
> performs roughly as expected, but slightly slower when served from
> RAID-5 (maybe 25% difference at most).
> - SSH and even serial console interaction on other shells feels much
> choppier than it used to be according to my memory with Squeeze while
> I was doing these benchmarks.
> - System is fine without this disk activity (I didn't try if network
> activity would have a similar effect, but just busylooping processes
> cause no trouble).
>
> Do you have a chance to try this on Kirkwood system, preferably with
> Marvell 6282, not 6281? Somehow I'm feeling that
> linux-image-3.0.0-1-kirkwood kernel is missing interrupts, or
> something. There is no indication of this on dmesg, though.
Also, when I perform RAID scrubbing with "echo check >
/sys/block/mdX/md/sync_action", I see drastically reduced performance
- down from 30-34 MB/s to 13 MB/s. Something has certainly changed.
-kirma
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