On Wed, Nov 19, 2008 at 7:16 AM, Carlos E. R.
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On Tuesday, 2008-11-18 at 16:42 -0800, James D. Parra wrote:
Trying to find why almost every process that requires IO has near 100% wait times.
Disk drives are SLOW!! Cpu's are FAST!!!! Accept it and optimize your process around that fact.
Even a simple 'cp' command has enormous wait times and doesn't appear at or near the top of the list when running 'top'. This was occurring when writing to a raid, but have tested writing to the system drive and the same thing occurs.
As expected, cp basically does nothing but tell the disk drive to do a bunch of work. Especially disk seeks take milliseconds, whereas cp can do its work in microsseconds. ie. For cp the CPU is typically 10 or hundreds of times faster than the disk.
Running the 'cp command copying a 19GB file from /tmp/file1 /tmp/file2 will take 50 minutes
Not normal.
Why not, have you benchmarked it? My working assumption is that copy from one physical drive to the SAME physical drive is about 10x slower than the same copy between 2 different drives. If true, then this would be about 190 GB / hr if it was between 2 different dirves. A very good speed. When moving big data sets I always think about the underlying physical drives and try to have the source and dest on different ones. If you want to test it on a single drive, at least use dd to do your benchmarking. dd if=/tmp/file1 of=/tmp/file2 bs=512 dd if=/tmp/file1 of=/tmp/file2 bs=4k dd if=/tmp/file1 of=/tmp/file2 bs=1M dd if=/tmp/file1 of=/tmp/file2 bs=1000M I bet you will see huge differences in speed among the above. Start with the 1000M bs and work down. I bet the 1000M case does the copy in less than 10 minutes. Greg -- Greg Freemyer Litigation Triage Solutions Specialist http://www.linkedin.com/in/gregfreemyer First 99 Days Litigation White Paper - http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf The Norcross Group The Intersection of Evidence & Technology http://www.norcrossgroup.com -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org