partition sizes

Adam Myrow amyrow at
Thu Nov 14 20:22:19 EST 2002

On Thu, 14 Nov 2002, Igor Gueths wrote:

> Hi justin. Well in terms of partition sizes, your swap partition is just
> at about the right size. You have 256 mb of ram, and the general rule is
> to have a swap partition double the size of your ram.

I guess this false information will continue to propagate forever.  It is
totally illogical.  As I explained before, the idea of requiring twice as
much swap as RAM goes back to a very early version of BSD Unix which
automatically allocated an equal amount of swap and RAM for an
application.  For example, with 256MB of RAM a program that needed 8MB
would get 8MB of RAM and 8MB of swap right off the bat.  In Linux and most
modern Unix and Unix-like operating systems, swap works as an extension of
RAM.  Swap is only used when either there isn't enough physical RAM to run
something or a program has been sitting there doing nothing for a good
while.  As somebody else stated, a process like agetty or mingetty that is
waiting for logins on a virtual console is a prime candidate to get
swapped out since it mostly sits and is taking up RAM.  My theory on swap
is to always have at least 128MB just in case you need it.  Even with only
32MB on my ancient computer, I seldom use more than 4 or 5MB of swap, but
if I didn't have that swap, I'd regret it.

As for splitting up the Linux partitions, there are advantages to it
especially on a big drive.  The classic argument in favor of it is that if
something goes out of control and starts eating disk space, you have a
better chance of not crashing because it filled up an important partition.
You're better off having something like that happen in /home if it's a
separate partition than if it fills up your root partition.  How many
partitions to have depends on what you are going to do.  If you are
running a server, you would likely want a separate /var partition since
server logs usually go there.  I personally prefer having /home and
/usr/local on there own partitions so that in the event of a disaster or a
major upgrade, you don't have to restore all that from backups.  On the
other hand, multiple partitions can make backups themselves more
complicated as some backup utilities like to do the partitions
separately.  You could also do them as one big backup with cpio or tar,
but I like to have the partitions in separate files as well to cut down
on time when restoring.

As to that last question about cylinder 1024, if you put Lilo in your
master boot record, it can boot from just about anywhere.  In some
configurations, you don't want to do this.  However, it works for me.  To
see where cylinder 1024 is on your drive, you can run the Linux version of
fdisk from an install disk and do a "p" command.  It lists the sizes of
partitions and the start and end cylinders.

As a last note, if you install Windows after Linux, it will happily
replace your MBR with its own.  I also think Windows should be first on
the drive as I think it may have problems booting from anywhere above 1024
cylinders.  Anybody know for sure about that?  I do know that any DOS
applications can't see anything above 1024 cylinders, so for example,
putting Windows 95 in DOS mode makes my second partition vanish.  Hope
this helps.

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