Odd iozone results
Posted Jan 30, 2012 2:48 UTC (Mon) by raven667
In reply to: Odd iozone results
Parent article: XFS: the filesystem of the future?
The mixed workload does random 4KB write IO - it even tells you that when it starts. Your workload doesn't fit in memory, so it will run at disk speed. 700KB/s is 175 4k IOs per second, which is about 6ms per IO. That's close to the average seek time of a typical 7200rpm SATA drive. Given that your workload is writing 8GB of data at that speed, it will take around 3 hours to run to completion.
IOWs, there is nothing wrong with your system - it's writing data in exactly the way you asked it to do, albeit slowly. This is not the sort of problem that an experienced storage admin would fail to diagnose....
in my experience the average server admin wouldn't be able to characterize or understand this issue. I've seen a lot of magical thinking from admins and developers when it comes to storage, sometimes for networking as well although the diagnostics tend to be better for that (wireshark, tcpdump).
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