Comment 319 for bug 620074
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#319 |
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4d1350f
(Get the code!)
(In reply to comment #304)
> ASUS P5K
> linux suse 2.6.29-53-default x86_64
You're running a kernel that is known to have high write latencies, and it doesn't appear that your fsync latency test is running in parallel with the dd. With 8GB of RAM, you likely need to change your dd to write out at least 10GB of data instead of 5GB.
(In reply to comment #305)
> Just tried dd if=/dev/zero of=bigfile bs=1M count=20k conv=fdatasync on
> 2.6.30-rc2 and top still shows iowait of 70% to 90%, on ext3 filesystem.
Your system *should* show high iowait when you're stress testing it like that. If it doesn't, you're not writing to disk as fast as it can handle it.
High iowait is normal and expected. It is not an indication of a problem.
What is not expected is high latency during those stress tests.
Ideally you should see sync latencies of less than a second - if latencies get higher than that you are likely using ext3 data=ordered or a broken kernel.
2.6.30-rc2 was just released - that should be used for future tests.