dstat reporting twice the actual disk activity?

[no_hope]

I noticed that dstat in the dsk/total column seems to report twice the amount of data transferred to and from disk.

For example, if I am transferring a file over 100Mbps network, scp will report about 10MB/s, dstat's network "send" column will report about 10MB/s, but the disk read column is reporting over 20MB/s. Similar things happens when I move data between drives. pv would report X MB/s and dstat will report 2X for both reads and writes. Copying to /dev/null is also reported to be at twice the rate it should be.

Am I missing something?

[Janne Pikkarainen]

I noticed that dstat in the dsk/total column seems to report twice the amount of data transferred to and from disk.

For example, if I am transferring a file over 100Mbps network, scp will report about 10MB/s, dstat's network "send" column will report about 10MB/s, but the disk read column is reporting over 20MB/s. Similar things happens when I move data between drives. pv would report X MB/s and dstat will report 2X for both reads and writes. Copying to /dev/null is also reported to be at twice the rate it should be.

Am I missing something?

I guess dstat reports the disk throughput in blocks per second, and as one block = 512 bytes, the reported transfer speed seems to be twice the rate it should be.