Re: Database server restarting

On Tue, 6 May 2003, shoaib wrote:

> When I login a console, I can see the prompt but after typing in login
> name system just don't respond it does not come to password prompt.

FYI, for future reference, this is generally referred to as being 
non-responsive, not hanging.  Hanging means the server has truly crashed, 
and is no longer answer pings, etc...  Usually hanging servers mean bad 
hardware.  Non-responsive servers often mean that you've increased the 
load too high for the server to handle, and it's busily swapping out 
resources left and right to try and stay up and running.

And there is NO reason to reboot a RedHat Linux 7.x box every night.  Mine 
routinely get 100 days of uptime between reboots, sometimes 200 days.  
Usually by then we're either upgrading to a new version or installing a 
new kernel and have to reboot.

Leaving the OS up is actually a good thing, as it keeps the buffers from 
getting cleared out.  Note that if all you want is for OS cache buffers to 
flush, just write a short c program that mallocs huge chunks of memory 
until you start swapping a bit.  But that's counter productive.  
Postgresql flushes buffers when it's writing, so you don't have to worry 
about dataloss, and the data in those buffers takes a while to load.

 11:42am  up 36 days,  1:20,  4 users,  load average: 0.27, 0.28, 0.32
195 processes: 194 sleeping, 1 running, 0 zombie, 0 stopped
CPU0 states: 21.0% user,  0.0% system,  0.0% nice, 78.0% idle
CPU1 states:  1.0% user,  8.0% system,  0.0% nice, 89.0% idle
Mem:  1543980K av, 1535472K used,    8508K free,  265928K shrd,   48872K buff
Swap: 2048208K av,  164524K used, 1883684K free                  871720K cached

Note the 870 Meg of cached data.  It takes my server at least a day of 
running before it can use the extra memory as cache, and rebooting it 
would make it start over.

Unlike Windows machines, Unix machines tend to run faster the longer 
they're left up.