Novell LINUX ENTERPRISE DESKTOP 11 - DEPLOYMENT GUIDE 17-03-2009 Deployment Manual page 170

12.1.4 More Partitioning Tips
The following section comprises a few hints and tips on partitioning that should help
you in taking the right decisions while setting up your system.
TIP: Cylinder Numbers
Note, that different partitioning tools may start counting the cylinders of a
partition with 0 or with 1. When calculating the number of cylinders, you should
always use the difference between the last and the first cylinder number and
add one.
Using swap
Swap is used to extend the physically available memory. This makes it possible to use
more memory than physical ram available. The memory management system of kernels
before 2.4.10 needed swap as a safety measure. In those times, if you did not have twice
the size of your ram in swap, the performance of the system suffered. This does not
hold true anymore as these limitations no longer exist.
Linux uses a page called "Least Recently Used" (LRU) to select pages that might be
moved from memory to disk. Therefore, the running applications have more memory
available and even their caching works more smoothly.
If an application tries to allocate as much memory as it can possibly get, there are some
problems with swap. There are three major cases to look at:
System with no swap
The application gets all memory that can be freed by any means. All caches are
freed, and thus all other applications are slowed down. After a few minutes, the
out of memory killer mechanism of the kernel will become active and kill the pro-
cess.
System with medіum sized swap (128 MB–512 MB)
At first, the system is slowed down like a system without swap. After all physical
ram has been used up, swap space is used as well. At this point, the system becomes
very slow and it becomes impossible to run commands from remote. Depending
on the speed of the hard disks that run the swap space, the system stays in this
condition for about 10 to 15 minutes until the out of memory killer of the kernel
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