The sys admin's daily grind: LUG Camp and Iotop

High-Altitude Euphoria

By Charly Kühnast

The 10th LUG Camp saw the Linux faithful trekking into the mountains. Around 120 Linux fans, including yours truly, met at a school youth hostel in Gschwend near Immenstadt (Figure 1). Nobody had to do without water: The hostel's own waterfall, fed by meltwater from even higher up, cooled the kegs of beer and even served as a shower for some hardy souls.

Figure 1: A talk on the topic of WLAN against a typical highland backdrop. LUG Camp 2009 pitched tent at an altitude of 800 meters at the end of May.

Although LUG Camp traditionally perceives itself more as a geek family gathering with the focus very obviously on fun, this doesn't mean a complete lack of content: Anybody with the necessary knowledge and desire could take an LPIC exam, and there were some really excellent talks. Incidentally, the thin mountain air of Gschwend didn't worry the participants in the least after the chili contest expanded their lungs to at least twice their normal capacity.

Iotop

Throughput, data this time, is also the domain of the tool that I will look at here. Iotop solves a problem that has often bugged me: The system is slow because its disks are running all the time, but I can't identify the process behind it. Iotop [1] gives me exactly this information.

The Python program needs at least kernel 2.6.20 with TASK_DELAY_ACCT and TASK_IO_ACCOUNTING enabled. When launched, the top line of the output shows the current I/O data rates for read and write access. Below this is a list of the input/output activity by process (Figure 2).

Figure 2: Iotop lists the disk activity of active processes.

Short Stories

The iotop -o command line makes the output more readable. In this mode, you only see the processes that are causing I/O right now.

To extend the refresh interval from 1 to 10 seconds, specify -d 10. Iotop's batch mode is really useful. The command line

iotop -o -b -d10 -n30 > io.txt

tells Iotop to write the last I/O status 30 times to a file named io.txt at 10-second intervals. This shows how data rates develop over a period of five minutes.

Conclusions

If your hard disk LEDs are permanently lit, Iotop is indispensable. For me, LUG Camp is equally indispensable - I've already registered for next year's event.