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Old 02-26-2010, 04:00 PM
John Doe
 
Default Temperature sensor

On Fri, Feb 26, 2010 at 11:00:21AM -0500, Bowie Bailey wrote:
> Does anyone know of a cheap temperature sensor that will work with
> Linux? I don't need a fancy monitoring appliance, I just want a simple
> sensor that I can connect to one of my monitoring servers to let me know
> if the server room is getting hot.

Sorry, only one I used years ago (Hot Little Therm) is discontinued...
But, unless you already checked, some servers have integrated "ambiant" temperature...
By example, on HP servers:
# /sbin/hplog -t
ID TYPE LOCATION STATUS CURRENT THRESHOLD
1 Basic Sensor I/O Zone Normal 114F/ 46C 149F/ 65C
2 Basic Sensor Ambient Normal 78F/ 26C 104F/ 40C
3 Basic Sensor CPU (1) Normal 91F/ 33C 203F/ 95C
4 Basic Sensor CPU (1) Normal 91F/ 33C 203F/ 95C
5 Basic Sensor Pwr. Supply Bay Normal 91F/ 33C 140F/ 60C
6 Basic Sensor CPU (2) Normal ---F/---C 203F/ 95C
7 Basic Sensor CPU (2) Normal ---F/---C 203F/ 95C

JD



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Old 02-26-2010, 04:01 PM
Benjamin Franz
 
Default Temperature sensor

Bowie Bailey wrote:
> Benjamin Franz wrote:
>
>> Bowie Bailey wrote:
>>
>>
>>> Does anyone know of a cheap temperature sensor that will work with
>>> Linux? I don't need a fancy monitoring appliance, I just want a simple
>>> sensor that I can connect to one of my monitoring servers to let me know
>>> if the server room is getting hot
>>>
>> There is a good chance that lm-sensors supports your servers with no
>> additional hardware needed. To configure lm-sensors, run
>> 'sensors-detect' as root. If your cpu/motherboard is supported you will
>> be able to read system temps directly either using SNMP or by scraping
>> 'sensors' output.
>>
>
> I'm looking for room temperature, not case temperature.
>
If your goal is simply to know when the server room is getting hot, the
difference doesn't matter. All you need to know is that it is warmer
than normal: The case temps will track room temps + some roughly
constant number of degrees.

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Old 02-26-2010, 04:12 PM
Les Mikesell
 
Default Temperature sensor

On 2/26/2010 10:46 AM, Paul Heinlein wrote:
>
>>>
>>>> Does anyone know of a cheap temperature sensor that will work with
>>>> Linux? I don't need a fancy monitoring appliance, I just want a
>>>> simple sensor that I can connect to one of my monitoring servers
>>>> to let me know if the server room is getting hot
>>>>
>>> There is a good chance that lm-sensors supports your servers with
>>> no additional hardware needed. To configure lm-sensors, run
>>> 'sensors-detect' as root. If your cpu/motherboard is supported you
>>> will be able to read system temps directly either using SNMP or by
>>> scraping 'sensors' output.
>>
>> I'm looking for room temperature, not case temperature.
>
> Some hardware provides SNMP-addressable information on the temperature
> of inbound air, not just case temperature. I realize that inbound
> temperature is not exactly the same as room temp, but it's a pretty
> good approximation in many case.

Yes, are you really that concerned about whether people in the room are
comfortable - they'll tell someone if they aren't even without gadgets.
If the room is getting hot, so will the equipment, so internal sensors
will show the trend, just offset by a bit of equipment heat. Most Cisco
equipment and higher end UPS's will have SNMP readable sensors that
monitoring programs can read, graph, and alarm on thresholds, and I
believe you can enable them on linux servers with the right snmpd.conf
settings.

--
Les Mikesell
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Old 02-26-2010, 04:57 PM
John R Pierce
 
Default Temperature sensor

Dominik Zyla wrote:
> But it'll not give information about temperature in server room.
>

actually, it sorta can. find the lowest reading sensor on the
system, probably one on the mainboard... use a manual thermometer to
read the intake air temp and calculate the delta.

i think you'll find under normal operating conditions that delta is
pretty constant if the server is under a reasonably consistent workload.



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Old 02-26-2010, 05:11 PM
Dominik Zyla
 
Default Temperature sensor

On Fri, Feb 26, 2010 at 09:57:52AM -0800, John R Pierce wrote:
> Dominik Zyla wrote:
> > But it'll not give information about temperature in server room.
> >
>
> actually, it sorta can. find the lowest reading sensor on the
> system, probably one on the mainboard... use a manual thermometer to
> read the intake air temp and calculate the delta.
>
> i think you'll find under normal operating conditions that delta is
> pretty constant if the server is under a reasonably consistent workload.

True.. We're also doing like this in some of server rooms. But sometimes
we had strange values. So this sort of stuff can be not good enough.

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Old 02-26-2010, 05:27 PM
Les Mikesell
 
Default Temperature sensor

On 2/26/2010 12:11 PM, Dominik Zyla wrote:
> On Fri, Feb 26, 2010 at 09:57:52AM -0800, John R Pierce wrote:
>> Dominik Zyla wrote:
>>> But it'll not give information about temperature in server room.
>>>
>>
>> actually, it sorta can. find the lowest reading sensor on the
>> system, probably one on the mainboard... use a manual thermometer to
>> read the intake air temp and calculate the delta.
>>
>> i think you'll find under normal operating conditions that delta is
>> pretty constant if the server is under a reasonably consistent workload.
>
> True.. We're also doing like this in some of server rooms. But sometimes
> we had strange values. So this sort of stuff can be not good enough.

If you can get graphs from two different pieces of equipment on the same
page you can pretty much see the trend. A single device might have a
fan go bad or something - but that should probably be fixed anyway. On
servers that have variable CPU power you might see temperature
variations depending on the load.

--
Les Mikesell
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Old 02-26-2010, 05:35 PM
Dominik Zyla
 
Default Temperature sensor

On Fri, Feb 26, 2010 at 12:27:59PM -0600, Les Mikesell wrote:
> On 2/26/2010 12:11 PM, Dominik Zyla wrote:
> > On Fri, Feb 26, 2010 at 09:57:52AM -0800, John R Pierce wrote:
> >> Dominik Zyla wrote:
> >>> But it'll not give information about temperature in server room.
> >>>
> >>
> >> actually, it sorta can. find the lowest reading sensor on the
> >> system, probably one on the mainboard... use a manual thermometer to
> >> read the intake air temp and calculate the delta.
> >>
> >> i think you'll find under normal operating conditions that delta is
> >> pretty constant if the server is under a reasonably consistent workload.
> >
> > True.. We're also doing like this in some of server rooms. But sometimes
> > we had strange values. So this sort of stuff can be not good enough.
>
> If you can get graphs from two different pieces of equipment on the same
> page you can pretty much see the trend. A single device might have a
> fan go bad or something - but that should probably be fixed anyway. On
> servers that have variable CPU power you might see temperature
> variations depending on the load.

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.

--
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Old 02-26-2010, 05:41 PM
 
Default Temperature sensor

Dominik wrote:
> On Fri, Feb 26, 2010 at 12:27:59PM -0600, Les Mikesell wrote:
>> On 2/26/2010 12:11 PM, Dominik Zyla wrote:
>> > On Fri, Feb 26, 2010 at 09:57:52AM -0800, John R Pierce wrote:
>> >> Dominik Zyla wrote:
>> >>> But it'll not give information about temperature in server room.
>> >>
>> >> actually, it sorta can. find the lowest reading sensor on the
>> >> system, probably one on the mainboard... use a manual thermometer
>> >> to read the intake air temp and calculate the delta.
<snip>> >>
>> If you can get graphs from two different pieces of equipment on the same
>> page you can pretty much see the trend. A single device might have a
>> fan go bad or something - but that should probably be fixed anyway. On
>> servers that have variable CPU power you might see temperature
>> variations depending on the load.
>
> 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.

Here's a question back: does the HVAC in the room allow monitoring?

mark

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Old 02-26-2010, 05:53 PM
Dominik Zyla
 
Default Temperature sensor

On Fri, Feb 26, 2010 at 01:41:00PM -0500, m.roth@5-cent.us wrote:
> Dominik wrote:
> > On Fri, Feb 26, 2010 at 12:27:59PM -0600, Les Mikesell wrote:
> >> On 2/26/2010 12:11 PM, Dominik Zyla wrote:
> >> > On Fri, Feb 26, 2010 at 09:57:52AM -0800, John R Pierce wrote:
> >> >> Dominik Zyla wrote:
> >> >>> But it'll not give information about temperature in server room.
> >> >>
> >> >> actually, it sorta can. find the lowest reading sensor on the
> >> >> system, probably one on the mainboard... use a manual thermometer
> >> >> to read the intake air temp and calculate the delta.
> <snip>> >>
> >> If you can get graphs from two different pieces of equipment on the same
> >> page you can pretty much see the trend. A single device might have a
> >> fan go bad or something - but that should probably be fixed anyway. On
> >> servers that have variable CPU power you might see temperature
> >> variations depending on the load.
> >
> > 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.
>
> Here's a question back: does the HVAC in the room allow monitoring?

It could be some problems with ventilation, I guess.

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Old 02-26-2010, 06:02 PM
"nate"
 
Default Temperature sensor

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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