Lukas Beeler's IT Blog

Another SMB topic, as most enterprises are obviously capable of doing this by the book.

Summer seems to be starting, with the days here getting warmer and warmer. A particular problem that seems to crop up every summer is servers shutting down or failing due to excessive temperatures. The tolerances of these machines to temperatures is actually quite low, even with redundant fans installed.

Most Small Businesses actually don’t follow any kind of strategy when choosing a place for servers, and usually try to ignore the AC problem – this works quite well when the new systems are installed during cold times.

While it might be possible to operate a server room without AC, this only works in rather rare circumstances:

• No windows, or very small windows
• Room is only during direct sunlight for a short time of the day
• A very small number of machines installed in the room (one or two)

So, in general you will need an AC. But what are acceptable temperatures in a server room? The ideal would be 22C during the entire year. But it’s possible to run a server in a bit hotter environment. These specs usually depend on the server itself. Consider that there is other temperature sensitive equipment in the room – tape drives, UPSs, etc.

Start reviewing the spec sheets of your server to see what is acceptable. Here is an example for an IBM System x3650:

• Air temperature:
  • Server on:
    10° to 35°C (50.0° to 95.0°F); altitude: 0 to 914.4 m (3000 ft). Decrease system temperature by 0.75°C for every 1000-foot increase in altitude.
  • Server off:
    10° to 43°C (50.0° to 109.4°F); maximum altitude: 2133 m (7000 ft)

As you can see, the maximum temperature during operation is 35C. With outside temperatures reaching this level during summer, an AC is almost always necessary. A UPS like the Powerware 9125 is specified to work from 0C to 40 C. This is a bit more generous than the x3650, but it’s still easy to get up to 40C with several servers in a room.

In order to figure out if you need an UPS, the best way to figure this out now is monitoring your server. If you are using IBM Director or HP Insight Manager, these tools already have this functionality integrated. I personally don’t like these two products (and they’re usually overdesigned for less than 10 servers). If you have an iLO or RSA II card in your server, you can use SNMP to get the temperature, write it to a file, and get a graph from this later.

I wrote a quick and dirty script to this. It runs on linux, but the same would be easily implementable in PowerShell or VB.

#!/bin/sh
while true ; do
        echo -n "`date +%s`;" >> ~/tempmon/machine
        snmpget -Onqv -c public -v 1 \
                machine.rsa.int.dataline.ch \
                SNMPv2-SMI::enterprises.2.3.51.1.2.1.5.1.0 |
                sed 's/"//g;s/Centigrade//;s/ //g' >> ~/tempmon/machine
        sleep 5m
done

Ugly? Yes. But it works fine. You can later load this “CSV” into Excel, and create appropriate graphs from the data. And get management to buy the AC before your servers die a fiery death. If you want to monitor this long term, you could integrate the appropriate values into cacti quite easily.

A sidenote about ACs from my personal experience: The same points as for servers apply – you get what you pay for. Buying self install ACs from Fust, MediaMarkt or some other chain in that direction won’t do you much good. Get a decent, two component AC, and let it get installed by a professional. This also avoids building damage. Also, let a professional size the system, provide him with the maximal output of your servers (measured in BTU), and then double that value just to be sure. Network managed ACs are usually not available for Small Business-acceptable pricing,