dd if=something of=somewhere bs=4K/1M/2M/4M count=testsize oflag=dsync
- To free pagecache:
12# echo 1 > /proc/sys/vm/drop_caches - To free dentries and inodes:
12# echo 2 > /proc/sys/vm/drop_caches - To free pagecache, dentries and inodes:
1# echo 3 > /proc/sys/vm/drop_caches
https://romanrm.net/dd-benchmark
https://www.thomas-krenn.com/en/wiki/Linux_I/O_Performance_Tests_using_dd