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Newsgroups: uk.comp.os.linux Date: 2002-09-22 04:28:05 PST
>>Just curious if people in this group leave their systems on >>all the time, or turn them off each day (providing you are not hosting >>a web server etc!) > > The two machines on my desktop are powered up and down, usually > several times a day. And they've lasted since 1995 and 1996, so > if one of them goes now, the saving I've made in power will be > hugely greater than the market price of a comparable replacement.
I doubt it.
Assuming you have an 'average' PC, you've got a 300W switch-mode PSU, rated at ~75% efficiency (most are better, but for the sake of argument, let's say it's not a "good" one). That means the absolute maximum power it will draw is ~400W. Actually this is an over-estimate since PSU's of the day were typically 200W, but for the sake of argument we'll use current figures…
Let's say you use the computer flat-out for 25% of the day, with it idling the rest of the time. I think this is a gross over- estimate - typical tasks are hardly a strain on computers, but again, for the sake of argument…
Let's assume that with the computer running flat-out, it completely maxes out the power suppy (again, an unreasonable over-estimate, but for the sake of argument…) Let's similarly assume that keeping the power flowing takes about 25% of the maximum the PSU can provide… again I think I'm being generous, but …
This means you draw 400W for 3 hours (assuming you sleep at night), and approx 100W that for the rest of the day. You use 100W all night. This is per-machine.
Your daily total of Kilowatt-Hours (kWH) per machine is therefore (3*0.4 + 21*0.1) or 3.3 kwH.
1995 is 8 years ago, so the total kwH since then is 8 * 365 * 3.3, or 9636 kWH. The price of a kWH is currently approx 5p, giving a total figure for the power used per machine of 9636 * 0.05 pounds, if the price of electricity has not risen in 8 years (not true!)
This gives a price for running each of your computers for 8 years of approx. 480 pounds, and this is a gross over-estimate, as pointed out (repeatedly :-)
The figure above doesn't take into account the *difference* between you using the machine, and you leaving it on either - you should really subtract from it how much power you actually used…
Hardly "hugely greater", and if the figures were not over-estimated, I think you'd find it's more like 250 quid.
Pedantically,
Simon. (who leaves his computers on…)
> Hardly "hugely greater", and if the figures were not over-estimated, > I think you'd find it's more like 250 quid.
Well, if the market value of a machine of that age is up to ~50 quid (as it was last time I looked on the uk computer marketplace newsgroup) then by your calculation that's a 400% difference.
> Pedantically,
Quite.
Nick Kew
> I do leave mine all the time, but would like to be able to spin down the > harddrives.
Worth noting that if you are using a journeling filesystem like ext3 or reiserfs then the drives won't be able to spind down using apm and if you spin them down manually with hdparm they will start right back up again.
Stuart Buckland
> >>Hard disk heads can also get dirty, > >>because they don't get accumulated dirt cleaned off on the landing > >>zone when they are powered on/off. > >> > > Heads on a hard disk get dirty?? I don't think so. > > I was curious about that myself. How exactly would the dust get into a > sealed container?
It's present when sealed, I suppose. "Sticktion" occurs when minute amounts of grease that accumulate on the drive heads cause the heads to adhere to the landing zones. When started up, the heads won't fly and the disk gets wrecked. This doesn't occur in drives powered down at least every few months because ridges in the landing zone clean the dirt off the heads.
I have read this in quite a few places, including several times in this group IIRC. Apparently it's a cause of drive failure in long-running servers, but not running one I haven't seen it myself.
Roger Leigh
> When started up, the heads won't fly > and the disk gets
whacked until it works again.
(This is unlikely to damage modern disks, but it should unstick the heads.)
Nix
> I have read this in quite a few places, including several times in
It's true that when turning off a disk that has been running non-stop for years it may not start again, but AFAIK the problem is in the bearings. Over time the lubrication migrates away from the running surfaces and under continual pounding by ball bearings at high temperature the chemical properties of the remainder change to a form of tar.
Dave Pickles