[CentOS] Temperature sensor

[Wade Hampton]

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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