Yet another swap question

aznium · 12-10-2005, 07:01 PM

I have a server running...and i stupidly forgot to add a swap partition to it when i installed it.
anyways, the hard drive (20 gig) contains one ext3 partition (also 20 gig)

my question is: lets say i run an intensive program that requires a lot of memory (ie 4 gig) . and the server only has 1 gig of physical memory, will the server crash if i run it? or just very slow performance?

solutions:
i do not have physical access to server - if anything goes wrong ... it will take a few days to get access to machine . and any downtime is unacceptable

1) resize the ext3 partition and add/mount a swap partition?

thanks

foo_bar_foo · 12-10-2005, 07:34 PM

yes it will crash
but first it will just run slow
Linux can use a file for swap

aznium · 12-10-2005, 08:12 PM

will the server crash? or will the program crash?

syg00 · 12-10-2005, 08:28 PM

Indeterminate I would think.
If it's a server, isn't either an unacceptable result ???.

As foo_bar_foo indicated, you can use a file in lieu of a partition for swap. In 2.6 the alledged performance penalty has been rectified. Even if you are on a 2.4 kernel, the penalty would be worth taking.
You have a simple solution that requires no outage - why are you dithering ???.

aznium · 12-10-2005, 08:53 PM

if the program crashes, my core services would not be affected (ie. apache, postfix, etc)

if the server crashes (as in the kernel in whole), my core services would go down with it ... which is bad bad bad

how would i use a file as swap?
create a file such as /swap and mount it just like a swap partition?

also, yes i am using a 2.6 kernel (2.6.14 series i think, or 2.6.13)

syg00 · 12-10-2005, 09:23 PM

Quote:

Originally Posted by aznium

if the program crashes, my core services would not be affected (ie. apache, postfix, etc)

You wish.
They would look like they have died if it takes something like 20 mins to get a response.

Quote:

how would i use a file as swap?
create a file such as /swap and mount it just like a swap partition?

Yep, have a look at tldp, (and the following section). It's old, but still valid - play with the sizes; multiple 2Gig files might be the best option.

aznium · 12-10-2005, 10:42 PM

thanks,

i have successfully created a swap file

to help others, wut i did was:

dd if=/dev/zero of=/swap-space bs=1M count=1024 #create a 1 gig zeroed in file (1megabyte * 1024)
mkswap /swap-space #convert that file to swap space
swapon /swap-space #enable it

that created an swap file of 1024 X 1M or 1 gig swap file