On 1/21/07, Tim Schmielau <[EMAIL PROTECTED]> wrote:
Note that these dd "benchmarks" are completely bogus, because the data doesn't actually get written to disk in that time. For some enlightening data, try time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024; time sync The dd returns as soon as all data could be buffered in RAM. Only sync will show how long it takes to actually write out the data to disk. also explains why you see better results is writeout starts earlier.
I am still getting better I feel: [EMAIL PROTECTED] ~]$ time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024; time sync 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 19.5007 seconds, 55.1 MB/s real 0m20.439s user 0m0.004s sys 0m4.535s real 0m4.625s user 0m0.000s sys 0m0.125s [EMAIL PROTECTED] ~]$ time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024 | sync 1024+0 records in 1024+0 records out 1073741824 bytes (1.1 GB) copied, 20.8707 seconds, 51.4 MB/s real 0m22.449s user 0m0.002s sys 0m4.922s Linux used here is not 2.6.20-rc5, but it's a FC6 2.6.19 binary. Shall post the results with 2.6.20-rc5. BTW, does the results vary with a customized kernel (configured w.r.t Processor & Hardware) than a generic kernel like FC6? Are there any other such test cases?
Tim
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