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UNTESTED CHARACTERISTICS
Although our methodology provides us with a very thorough means of testing
for drive noise, our methodology by no means tests every characteristic
of hard drives. Among the characteristics we do not test:
- Performance
- Heat dissipation
- Reliablility
We've already mentioned why we don't run performance tests: Generally we don't believe they are all that significant; many other sites do such testing extensively. Properly testing the performance of a hard drive is a complex and labor-intensive
task. This article
on the methodology for testing HDD performance by StorageReview.com details
the many factors that must be considered when evaluating a hard drive's performance,
including the intended use, interface, throughput, and seek times. Running performance tests in addition to noise tests simply demands too much of our time and effort. We're interested in providing acoustic information not available elsewhere.
While designing our test methodology, we seriously considered devising a test
for drive heat dissipation. Ultimately, we decided against including such testing
in our reviews for four reasons:
- To paraphrase a SPCR reviewer: This is SilentPCReview, not
CoolDriveReview.
- Hard drives do not conduct heat in the same way. Testing different drives
in a way that is both fair and repeatable is extremely difficult.
- The temperature reported via the internal HDD temperature diode is probably more
accurate than anything we could measure with external sensors, but not all drives are equipped with temperature diodes and not all temp diodes are accessible with the software we have (SpeedFan, DTemp, etc.).
- We do not know of any way to check or calibrate the accuracy of internal HDD temp diodes.
- Power draw is the biggest determinant to HDD temperature, and as we've already detailed, this is tested for idle and seek states.
Ultimately, there are only two ways in which we consider HDD heat to be relevant:
1. Effect on Case Cooling: The amount of heat produced by a hard drive is roughly proportional to the
amount of power it consumes. Power consumption varies very little between drives,
perhaps by four watts at most across all models of a given form factor and spindle
speed. Even the difference between a 2.5" notebook drive and a 10K RPM 3.5" drive is only in the range of 10-15W,
a negligible amount when the CPU and the VGA card can each draw >100W.
There is not enough difference between different hard drives
to justify testing power consumption. In practical terms, the total amount of
heat that a hard drive adds to a case varies only minimally between different
drives.
2. Effect on Reliability: This is something even certified product testing enterprises
such as UL or CSA have trouble with. It requires a huge number of samples and
extensive testing tools, neither of which are practical for SPCR. In fact, the
best reliability info is probably obtainaible only from large distributors'
historical records after a product has been sold for a while. Everything else
is conjecture and informed guesswork.
In general, a drive's operational temperature is affected by
spindle spin speed and number of platters: The higher they are, the
hotter the drive will tend to run. Most modern HDDs are rated for safe operation
up to 60°C. This seems a very high temperatrure, and surely, drive reliability
must be adversely affected by running too close to the maximum temperature for
any length of time. We would suggest 45~50°C as a safer maximum temp for end
users who have access to the same temp monitoring tools that we have. If you are more cautious, set a lower maximum HDD temp target, monitor the drive temps, and use manual or thermally controlled active cooling to keep the drive temps down.
TESTING NOISE-REDUCTION PRODUCTS
In addition to testing hard drives, SPCR also reviews products that are designed
to reduce hard drive noise. No matter what technique these products use to reduce
drive noise, our approach to reviewing them is the same: Use the noise reducer with a moderately
noisy drive to conduct our standard
acoustic and vibration tests, then compare the results with and without the noise reducer. In some cases we may
try more than one drive, perhaps choosing one with very high vibration and another
with high noise. The obvious thing we're looking for is the difference the noise
reducer makes.
Most noise reduction products tend to enclose a hard drive or mount them to the case in a different way. Often, the operating temperature of the drive may be affected because of reduced heat conduction to the case compared with standard 4-screw mounting. For this reason, we will also record temperatures of the drives with and without the noise reducing product. The temperatures will be read from S.M.A.R.T. We are interested in the relative change, not the absolute value reported.
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