[LINK] Leave on, or turn off?

Richard Chirgwin rchirgwin at ozemail.com.au
Fri Dec 1 07:07:20 AEDT 2006

Kim Holburn wrote:
> On 2006/Nov/30, at 1:54 PM, grove at zeta.org.au wrote:
>> I tend to leave my gear on 24x7 unless there's a storm approaching
>> or if it's a heatwave prediction - we don't have air conditioning at 
>> home!
>> Most hard drives have MTBF ratings (Mean time between failure) of 
>> values exceeding 80,000 hours or more.   These ratings are determined 
>> by running the disks at sea level and room temperature (about between 
>> 20-30c) constantly at full power.   If you run your disks at higher 
>> temperatures, you start to get a 4x drop in life expectancy
>> as you get closer to 40c.
>> With electronics, it's the capacitators and high energy components 
>> likely to go first.   Generally the power supply is the thing that is 
>> likely to become unstable as the capacitators start to age or dry 
>> out.   Fans are the worst - cheap nasty fans with no grease in the 
>> bearings are the things that lead to more failures than anything 
>> else.   Lose the fan and it silently raises the internal system 
>> temperature until things start to go wrong!
> I don't see why capacitors should be a problem but there was in the 
> last few years a whole batch (from a particular factory? In China?) 
> that were bad and all had to be replaced, millions of them.  Would 
> this have skewed the figures? 
Electrolytic capacitors use a "wet" (relatively) chemical between the 
plates. These *do* deteriorate over time as the electrolyte dries. This 
is more relevant to the power supply than the motherboard - the tiny SMD 
capacitors use a ceramic dielectric ... and anyone who's spent time with 
a soldering iron knows the smell of a dead capacitor giving up its ghost 
in smoke!

To the main question, I'm with the don't-waste-energy lobby; I have not 
seen any significant difference in the life of a home machine that gets 
switched off overnight. A PC becomes obsolete long before power-cycling 
kills it... If we assume that there's 5 million PCs in Australian homes 
(an invented statistic), at an average 5W per PC (also invented) on 
"night" cycle, for 16 hours  a day (a guess at "idle" time in standby 
mode, allowing for wide variation in individual usage), we get 25 x 16 
MWh or 400 MWh just to get quick startup.

So you could argue that slow-loading operating systems are a serious 
energy waster. If the PC started as quickly as a TV, people would not 
feel they had to leave them switched on all the time...

> About 5 years ago I and a colleague installed a group of servers with 
> no moving parts at all.  Mini-ITX systems with OS on flash memory, no 
> fans.  They are still working perfectly.  We have had one power supply 
> failure in that time and a couple of them are getting a little 
> underpowered as needs grow but that's it.  We had one problem getting 
> them working initially as most linux systems use human input and hard 
> disk latency to provide entropy and these had neither.
> Getting rid of fans is the key, it's also the key to having any home 
> servers that are bearable to share a house with but it's getting 
> harder with modern CPUs.
> -- 
> Kim Holburn
> IT Network & Security Consultant
> Ph/F: +61 2 62577881 M: +61 417820641
> mailto:kim at holburn.net  aim://kimholburn
> skype://kholburn - PGP Public Key on request
> Democracy imposed from without is the severest form of tyranny.
>                           -- Lloyd Biggle, Jr. Analog, Apr 1961
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