Date: Sun, 6 Feb 2005 00:13:38 +0100 From: Anthony Atkielski <atkielski.anthony@wanadoo.fr> To: freebsd-questions@freebsd.org Subject: Re: Leaving a Computer Running ? Message-ID: <15210109162.20050206001338@wanadoo.fr> In-Reply-To: <200502051745.25937.hindrich@worldchat.com> References: <200502051745.25937.hindrich@worldchat.com>
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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 continuously. 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. -- Anthony
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