[CentOS] Swap Considerations

Tue Feb 27 02:48:59 UTC 2007
Feizhou <feizhou at graffiti.net>

Mike McCarty wrote:
> I am considering installing CentOS 4.4, and am interested in
> how best to set up. I have been using FC2 and helping administer
> a Debian machine for a few years, but do not consider myself a
> Linux guru.
> 
> My current set up uses a /swap partition which is 2x my memory
> size

This is a completely false premise that has no basis in Linux or even in 
  verions of Solaris after SunOS4. Only SunOS4 *REQUIRED* swap be twice 
the amount of RAM due to how its VM was implemented. The best of part of 
this is that this is actually a part of the 'knowledge' that the LPI 
examinations will examine you on.

With regards to swap, on servers you want to tune things such that swap 
is NEVER used but do create some swap space to handle edge cases. On 
desktops, create as much swap as you wish to handle firefox, thunderbird 
or whatever memory hungry GTK application you have. Of course, the more 
RAM you have, the merrier.

> 
> I'm also interested in whether it be reasonable/desirable to
> make /home, /tmp, and /var be on a separate partition. I have heard
> arguments on both sides, some claiming that with ext3 the system
> won't become unbootable because of /tmp filling up.

ext3 reserves blocks and inodes for root so it is true that /tmp filling 
up will not prevent boot up to an extent. You might find it necessary to 
make sure /var is not filled up if it prevents any critical services 
from starting. Putting /home on a separate partition makes it easier to 
upgrade the OS without having to move data around. If it were possible 
to make / read only, I would definitely put /tmp on a separate partition 
and just use ext2 for it.

I would therefore put at least /home and /var on separate partitions if 
it were a server where /home had data. If not, /var will be on its own. 
If it were my home desktop, /home definitely gets its own partition.