On Mon, 7 Jun 1999, Vincent Diepeveen wrote:
> continuing the off topic. How many of you guys *ever* reboot?
>
> I'm used to turn off my computer every night, except for the dual PII-450,
> which runs test after test, and i must reboot it to be able to test
> under NT, next day i test under linux.
>
> All other computers (where i do development at and such),
> laptops etcetera get turned off when i get to bed.
>
> How're you dudes handling this?
>
> When i ask here a few at the internet i get the reply: "we never
> even reboot it"...
There is no reason to reboot a properly installed linux (or other unix)
box. Indeed, there are excellent reasons to not reboot them and
especially not to power cycle them.
Don't Power Cycle: This is because the greatest "stress" a system
undergoes occurs during the actual initial power up. Cold things become
hot. There is an inevitable inductive power surge. Hard disk failure
is many times more likely to occur at a powerdown/powerup -- perhaps
half the failures I've experienced have occurred when a disk spun down
and just "froze" or refused to spin back up again. If one compares the
TIMES involved (powerdown being very rare compared to the extremely long
runtimes in between) one must conclude that the actual probability
density of failure is thousands or more times as high during powerup.
Memory, fans, power supplies themselves -- they all hate being power
cycled.
Recommendation: Minimally leave your systems on all the time, perhaps
with a power saver mode on your monitor. I like to keep my desktops on
a UPS, even, so that they are both well-protected against power surge
and protected against the annoying 10-15 second power glitches that
happen way too often in my neighborhood (especially during the summer
and thunderstorms). Sure, this costs a few cents a day in extra power
for a desktop, but if your system is in a cluster (especially if it is
in a beowulf) it is probably in use all the time anyway.
Don't Reboot Them: Why reboot? Linux (again, when properly installed
and maintained) is awesomely stable. It won't crash, its performance
won't degrade as memory doesn't leak, and as long as it's up it doesn't
stop logging things, it remains network connected, and people can rely
on the system being there and accessible. In most professional
workstation LANs or clusters (running linux or some other Unix flavor)
the systems get rebooted only when there is a real reason for it -- a
kernel or major library or distribution upgrade, a (rare) system crash,
after hardware maintenance. Users can then rely on these machines being
accessible at the console or via the network 24x7x365 (or nearly so),
and the system logs represent a continuous record of activity over this
entire interval or whatever interval systems persons select as a
monitoring window.
This is opposed, of course, to WinXX; some (a few) WinXX system
configurations are reported to be stable (if you don't use them too
hard) but most folks report that they crash spontaneously anywhere from
once or twice a day to at most once or twice a week, depending on usage.
If using a system with a bad memory leak, it may even be therapeutic to
reboot after running anything taxing just to ensure that a crash is less
likely with the next process or task one undertakes.
Recommendation: Bag Win NT altogether (I know, I'm sure that you can't
and have some good reason for running it, but still...) and leave your
systems running linux all the time. I would make a modest exception for
laptops -- as a practical matter they get moved and rebooted and power
cycled a lot, and have hardware and firmware to support the volatility.
Even a laptop that doesn't actually get carried around I would leave
"on" all the time -- my laptop will just shut itself down a major
component at a time if it isn't actively running anything -- and most
laptops have "suspend" modes that save their active state to either disk
or memory and shut down all the way or part of the way.
Note that DUAL (linux-smp, non-laptop) systems cannot use APC features
in the kernel, but other desktop systems may be able to use power-saving
features in the BIOS via the kernel when the systems are idle. Again, I
wouldn't hesitate to use these features if you like although I
personally don't mess with it.
rgb
Robert G. Brown http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567 Fax: 919-660-2525 email:[EMAIL PROTECTED]
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