Leaving a Computer Running ?

Anthony Atkielski atkielski.anthony at wanadoo.fr
Sat Feb 5 15:13:40 PST 2005

Peterhin writes:

P> Is it better to leave a computer (a stand alone) running continuously or
P> is it OK to shut it down at the end of the day.?

An age-old debate.

Advantages of leaving the computer running:

- Electronic components are not subject to thermal stress of start-up
and shutdown.  Not usually an issue, but it might have a slight effect
on life expectancy (although life expectancy for non-moving parts is
often far beyond the time one would expect to keep the system).

- Moving parts are not subjected to thermal and mechanical stresses of
starting and stopping.  For example, disk drives and fans are under less
stress during continuous running than they are at the moment when they
start and stop.  Failures are more likely to occur when a mechanical
part is started up than during continuous operation.

- The system is available and usable 24/7.

Advantages of cycling the computer each day or shift or whatever:

- Less power consumed; the savings depends on the duty cycle chosen.

- Potentially less wear and tear on mechanical parts.  They don't wear
at all when they are not running, whereas continuous running always puts
some amount of wear on them, however small.  But this is a balance
between the additional wear and tear incurred when you first start up or
shut down a mechanical part, and the much lower wear of something that
runs continuously but for long periods.

- Time-related problems go away, if software bugs cause any such
problems (memory leaks and so on).  This is not normally an issue with
FreeBSD, which can run for years at a time without problems, but it is
sometimes an issue with specific application software packages, if they
are poorly written.

P> I remember years ago someone mentioned that it is better for the
P> circuitry to leave it running.

Yes.  If it runs for 48 hours, it will probably run forever.  Running it
continuously keeps it thermally stable and may extend life.  This
assumes, however, that the circuitry is kept at a sufficiently cool
temperature.  Circuits that are running too hot may fail sooner if they
are operated continuously.  Use lots of fans if you run your system

All of this concerns only the CPU.  The rules for monitors have
traditionally been different.

CRTs should be shut off if they are not going to be used for an extended
period (such as all night); the exact duration of an "extended period,"
though, is a matter of great debate.  It's also arguable that putting
CRTs on standby instead of shutting them off completely may be
preferable (for reasons similar to those cited above for continuous
running of electronic circuits--thermal shock, etc.).  Screen savers are
a good idea when they CRT isn't being used, too, when the CRT is on.

LCDs are less problematic.  They should be shut off if you aren't going
to use them for a while, in order to preserve the backlight, which is
the main point of failure over the long term.  The duration of "a while"
is again a matter of some debate, but it is probably a shorter duration
than that for CRTs, because the wear and tear from being turned on and
off is lower for LCDs than for CRTs.  Conversely, however, LCDs suffer
less from extended continuous operation.  Images don't burn into the
screen, usually, and there are no phosphors in the front of the display
to wear out.  Screen savers are not necessary.

I have my LCD monitor set to go to standby after 60 minutes. On my CRT
monitor, I've had the standby time set to 2-3 hours at least, and unless
the monitor is relatively new, I never shut it off (I leave it in
standby instead). Inexpensive LCD monitors of limited importance (simple
text displays and the like) can be left operating all the time, since
they consume very little power and image quality is not critical (it
will deteriorate over time, but it will be years before they get dark
enough to no longer be useful for simple text display).  The console
monitor on my FreeBSD system, for example, is on pretty much all the
time, unless I plan to leave the area for the day or night, in which
case I usually switch it off.


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