HP Proliant MicroServer

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COOLING, FAN SPEED, POWER

Normal fan speed monitoring proved unachievable. Although the fan RPM showed up in the BIOS, no software utility could access the sensor in MWS 2008, or later, in Windows 7. The SPCR forum discussion about the MicroServer pointed to a reason why this might be so. Although the HP uses a 4-pin WPM fan, the pinout configuration is non-standard. The software utilities are programmed to read the on-board terminals in a standard configuration, thus cannot get the data correctly from the HP board.

We resorted to tagging one of the blades of the fan with a piece of white plastic tape so that it could be monitored optically with an IR tachometer or calibrated strobe through the back panel grill while the system was running, under different loads. This was a slightly tedious task.

Prime95 was use to stress the CPU. Various tools to stress the HDDs were tried, but we found none that could work all the drive at once, for any length of time. HDD Scan was identified as the most promising tool for our purpose, but again, it could not run any high stress test on the drives simultaneously. Even when run for more than an hour on just one drive, none of the utilities raised the HDD temperature beyond 37°C, the highest seend during Prime95 testing.

Windows 7 was installed, on a WD Green drive, simply to expedite testing. The security features in MWS Server 2008 makes it odious to turn the system on/off as many times as we must do in our intensive hardware testing. All the hardware montoring runs on MWS Server 2008 as well as on Windows 7; the same temperature results were seen in both OSes.

All of the Prime95 results were recorded after 60 minutes of continuous load.

HP MicroServer: Cooling Results
State
HDD*
CPU
AC
Fan RPM
SPL
with 2 Seagate Barracuda 7200.12 160 GB drives
(MS Windows Server 2008)
idle
32°C
34°C
34W
1080
23 dBA
Prime95
32°C
52°C
46W
1080
23 dBA
with 2 WD Green 2TB AV drives
(Windows 7)
idle
27~31°C
28°C
25W
1080
23 dBA
Prime95
28~32°C
52°C
37W
1080
23 dBA
with 4 WD Green 2TB AV drives
(Windows 7)
idle
28~31°C
28°C
37W
1080
24 dBA
Prime95
30~33°C
53°C
54W
1080
24 dBA
* The temperatures of the hottest and the coolest drives.

The 120mm fan starts at an elevated speed for a few seconds (under 10) when the system powers up, but it quickly settles down to a slower speed. In MWS 2008, the fan speed never changed in any of our testing, staying at a constant 1060~1100 RPM. The room temperature never exceed 24°C throughout the testing; it's possible that in hotter weather, with hard drives that draw more power, the fan could speed up. This aspect was not checked. The low temperatures suggest that the 120mm fan is providing much more airflow than is actually needed in most conditions.

The 40mm fan in the power supply might have sped up or down a bit during testing, but it was difficult to be sure with the hard drives and the 120mm fan all running. The small fan obviously did not introduce much — if any — audible noise.

One important note: Stopping the 120mm fan or unplugging its connector from the motherboard immediately shuts the MicroServer down. The safety-conscious speed sense feature appears to be undefeatable.

The component temperatures remained perfectly safe under high load. Hard drives are specified for safe operation to 55~60°C, and the AMD Neo CPU is rated for 95°C maximum, so there is plenty of headroom for much hotter conditions.

The power draw of the system is quite modest. With two WD Green drives, the power draw ranged 24~35W in normal use, with the average not much higher than 32W. With the more likely 4-drive setup , it went up about 10W, to around 40~43W average.

Surpringly,with the two Seagate Barracuda 7200.12 160 GB drives, the server idled (in MWS 2008) 9W higher than the two WD Greens. Peak power went up by the same amount, so it seems clear that the Barracudas are the cause the of extra power consumption. However, note that the idle CPU temperature in MWS 2008 was some 6°C higher than in Windows 7. So...

Windows 7 w/ 2 WD Green & 2 Seagate 7200.12 drives
State
HDD*
CPU
AC
Fan RPM
SPL
idle
32~35°C
35°C
42W
1080
23 dBA
Prime95
34~35°C
53°C
54W
1080
23 dBA
* The temperatures of the hottest and the coolest drives.

Another test was run, this time with the Window 7 loaded WD Green as the boot drive, another WD Green and the two Barracudas. This showed 5W higher idle power than with all 4 WD Greens, about what you might expect. CPU activity at idle was virtually zero as in all the previous tests. But the power draw at full CPU load was the same, which is odd. We expected the extra power for the HDD to add to the total AC power at high CPU load, too.

The best way to resolve this little puzzle would be to install Window 7 on one of the Barracudas, and MWS 2008 on one of the WD Greens, and recheck the power with both... but at this point, the exercise became too exhausting. Suffice it to say that most SPCR readers are not interested in any drives that sound like these Barracudas, and the overwhelming HDDs of choice for most users will be the Samsung, WD or Seagate "eco" drives which run quieter and only a bit slower at 5400 or 5900 RPM.



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