Hi, I'm running centos-4.4 on an SMP system with 4 dual core opterons (2.4 GHz), and 16 GB memory. The disk drives are 500 GB SATA-Drives.Wondering about times for dd command performance and rm command performance in an empty machine (the filesystem has been made with "mkfs.ext3 /dev/sd...", nothing more)
1. Making a new 3 GB (1024 x 3megabytes blocks) file with dd needs 10.18 sec wallclock time: taskset 1 time dd if=/dev/zero bs=3M count=1024 of=~backes/xxxxx 1024+0 records in 1024+0 records out 0.00user 10.02system 0:10.18elapsed 98%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (0major+187minor)pagefaults 0swaps 2. Repeating the same for 3 times: taskset 1 time dd if=/dev/zero bs=3M count=1024 of=~backes/xxxxx 1024+0 records in 1024+0 records out 0.00user 11.88system 1:05.26elapsed 18%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (0major+187minor)pagefaults 0swaps taskset 1 time dd if=/dev/zero bs=3M count=1024 of=~backes/xxxxx 1024+0 records in 1024+0 records out 0.00user 12.19system 1:04.43elapsed 18%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (0major+187minor)pagefaults 0swaps taskset 1 time dd if=/dev/zero bs=3M count=1024 of=~backes/xxxxx 1024+0 records in 1024+0 records out 0.00user 11.85system 1:09.45elapsed 17%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (0major+187minor)pagefaults 0swaps The wallclock times increase considerably and vary between 1 min 4.4 sec and 1 min 9.5 sec . Now removing the file needs a wallclock time of 46.7 secs: taskset 1 time rm -f ~backes/xxxxx 0.00user 2.16system 0:46.77elapsed 4%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (0major+166minor)pagefaults 0swaps Can somebody explain this weird behaviour. All comments are welcome. Regards -- Joachim Backes <joachim.backes@xxxxxxxxxxxxxx> University of Kaiserslautern,Computer Center [RHRK], Systems and Operations, High Performance Computing, D-67653 Kaiserslautern, PO Box 3049, Germany -------------------------------------------------- Phone: +49-631-205-2438, FAX: +49-631-205-3056 http://hlrwm.rhrk.uni-kl.de/home/staff/backes.html
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