[CentOS] Temperature sensor

Chris Geldenhuis chris.gelden at iafrica.com
Sat Feb 27 05:36:25 UTC 2010

Wade Hampton wrote:
> Try the Dallas/Maxim 1-wire system.  They have serial port
> controllers with an RJ11 jack so you can use a phone cable
> to the sensor.  I got one of their temp sensors and a cheap
> RJ11 jack from Radio Shack and had a remote temp sensor.
> They use a simple serial protocol and some of the controllers
> are "smart" like the DS9097U $28 or so for the controller:
>   http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2983
>   http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2923
> For temperature DS28EA00:
>   http://www.maxim-ic.com/quick_view2.cfm/qv_pk/5355
> On Fri, Feb 26, 2010 at 2:02 PM, nate <centos at linuxpowered.net> wrote:
>> Dominik Zyla wrote:
>>> You have right. While you checking sensors from few machines, you can
>>> see the trend. Gotta think about changing the way of temperature  monitoring
>>> here.
>> Myself I wouldn't rely on internal equipment sensors to try to
>> extrapolate ambient temperature from their readings. Most equipment
>> will automatically spin their fans at faster RPMs as the temperature
>> goes up which can give false indications of ambient temperature.
>> I do monitor the temperature of network equipment, but also have
>> dedicated sensors for ambient readings. Already saved us some pain
>> once, opened up a new location in London last year and the ambient
>> temperature at our rack in the data center was 85+ degrees F. The
>> SLA requires temperature be from 64-78 degrees. Alarms were going off
>> in Nagios.
>> The facility claimed there was no issue, and opened up some more
>> air vents, which didn't help. They still didn't believe us so they
>> installed their own sensor in our rack. The next day the temperature
>> dropped by ~10 degrees, I guess they believed their own sensor..
>> http://portal.aphroland.org/~aphro/rack-temperature.png
>> People at my own company were questioning the accuracy of this
>> sensor(there was only one, I prefer 2 but they are cheap bastards),
>> but I was able to validate the increased temperature by comparing
>> the internal temp of the switches and load balancers were
>> significantly higher than other locations. Though even with the
>> ambient temperature dropping by 10+ degrees, the temperature of
>> the gear didn't move nearly as much.
>> The crazy part was I checked the temperature probes at my former
>> company(different/better data center) and the *exhaust* temperature
>> of the servers was lower than the *input* temperature from this
>> new data center. Exhaust temperature was around 78-80 degrees,
>> several degrees below the 85+.
>> It seems the facility in London further improved their cooling
>> in recent weeks as average temperature is down from 78 to about
>> 70-72 now, and is much more stable, prior to the change we
>> were frequently spiking above 80 and averaging about 78.
>> Also having ambient temperature sensors can be advantageous in
>> the event you need to convince a facility they are running too
>> hot(or out of SLA), as a tech guy myself(as you can probably
>> see already) I am much less inclined to trust the results of
>> internal equipment sensors than a standalone external sensor
>> which can be put on the front of the rack.
>> nate
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