PostgreSQL 10 High Performance - Third Edition

iostat

The data vmstat gives is a total across all devices on the system. If you want totals per disk device instead, you need to use iostat for that.

On Linux, iostat defaults to slightly different behavior than vmstat. When it uses block, it means a 512 byte chunk of data, not the 1,024 bytes chunk vmstat uses. You can switch iostat to use kilobytes instead of using iostat -k, or you can just divide all the figures by two in order to get them on the same scale. Here's an example of the same data shown both ways:

$ iostat 
Device     tps Blk_read/s  Blk_wrtn/s  Blk_read  Blk_wrtn
sda1      0.07       3.29        0.24   1579784    115560
$ iostat -k
Device     tps  kB_read/s   kB_wrtn/s   kB_read   kB_wrtn
sda1      0.07       1.64        0.12    789892     57780

Since not all Unix versions will have the ...