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In Linux, the dd command can be used for simple I/O performance measurements as follows:

$ dd if=/dev/zero of=/root/testfile bs=1G count=1 oflag=direct
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB) copied,
32.474 s, 33.1 MB/s

Here the test took 32.474 seconds to run and 33.1 MB/s was the actual disk speed. Don’t forget to delete the test file when finished.


  • if: input file;
  • of: output file;
  • bs: sets the if and of sizes to bytes; block size (base 10 integer, 1G=1024×1024×1024 bytes = 1.073 GB);
  • count: number of blocks (1 means that 1 block of 1G is copied);
  • oflag=direct: uses direct I/O data, avoiding the buffer cache; and it speeds up the process 1.

Via enki.com.

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