===== What is this? =====
My notes on basic i/o benchmarks on linux/unix systems.
Writing a file without sync is fast ofcourse:
time dd if=/dev/zero of=file bs=512M count=1
So sync should be used, using one of these variants:
sync; time bash -c 'dd if=/dev/zero of=file bs=512M count=1; sync'
time dd if=/dev/zero of=file bs=512M count=1 oflag=direct
# capturing data
for i in {1..11}; do time dd if=/dev/zero of=file bs=1G count=6 oflag=direct 2>&1; done | tee time.txt
vmstat 10 | tee vmstat.txt
iostat -x 10 sda2 | tee iostat.txt
# calculating average time:
# cat time_ht |grep real|sed -e 's,.*m,,' -e 's,s,,' | \
# awk '{if(min==""){min=max=$1}; if($1>max) {max=$1}; if($1< min) {min=$1}; total+=$1; count+=1} END {print total/count, min, max}'
# suming up wait from vmstat
# manually removed entries at beginning/end of file that were bevore/after the dd run
# cat vmstat_ht |egrep -v '^procs|^ r b'|awk '{print $16}' | \
# awk '{if(min==""){min=max=$1}; if($1>max) {max=$1}; if($1< min) {min=$1}; total+=$1; count+=1} END {print total/count, min, max}'