On my RHEL 4 machine, I was downloading a huge file (2.5GB)..I was checking the output of vmstat and was especially curious about seeing the disk IO using bi and bo. I know iostat is a better tool suited for this but didn't have it installed on this machine.

Anyways, I was expecting bi (bytes in) to be high during the download but found the exact opposite...bo (bytes out) was very high during the download where as bi was mostly 0 with occasional numbers??

Also, without iostat, is there a better tool than vmstat that is available Out of the Box in a Red Hat machine?

2 Answers 2


The bi/bo figures are for block devices. Conventional network adapters are not block devices, so network I/O doesn't show up there; it doesn't show up in iostat either.

The high bo values come from writing the downloaded data to your disks. "Out" data going to the device, "in" for data coming from it.

For monitoring network activity, you could look at iptraf-ng (ncurses-based) or ntop (web-based), but I doubt they'll be installed on your system if iostat isn't - just ask your friendly sysadmin to add the required packages :)


Vmstat command provides virtual Memory statistics. If you check vmstat command then visit this link.

You can check downloading speed by netstat commmand as well. But for option, I need to check this command again. Please check for netstat command might it will help you.

There is one link..might it will help you. Click Here

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