Swap space location and SELinux

James Wilkinson fedora at aprilcottage.co.uk
Mon Nov 27 17:44:04 UTC 2006


sport wrote:
> Are you sure you can put swap space on LVM?  I have never done it, and
> think it may be a bad idea anyway.  You want the fastest partition or
> partitions to be swap, and usually I put it on a primary partition.

Depends.

 1. With today's memory prices, many people will have "enough" RAM that
    they don't usually use swap, and it's just there for use in
    emergencies. In that case, there's not much point in worrying about
    swap speed.

 2. Megabytes per second is very often a *lousy* measurement of disk
    speed -- it doesn't tell you what you want to know.

    It's fine if you want to transfer large files from the disk
    sequentially (megabytes of data or more). But many disk access
    patterns involve many short accesses (say, a few kilobytes). In this
    case, the time to read the data off the disk will be dwarfed by the
    time it takes to get the disk heads to the right place. So for high
    performace, you want to minimise the access time. And the bit of the
    disk with the lowest access time is right next to where the heads are
    at the moment.

    So you may well want the swap to be near the data you're using,
    rather than at one end of the disk.

> Also, you can shut off selinux by passing the kernel parameter selinux=0
> I don't know off hand how to pass kernel parameters to an installation
> kernel, but I'm pretty sure it can be done.

http://fedora.redhat.com/docs/fedora-install-guide-en/fc5/ch-beginninginstallation.html

You'll all be familiar with the boot screen of a Fedora CD-ROM: you just
type in (for example)
linux selinux=0
plus anything else you think will be needed.

James.

PS: the mailing list guidelines discourage top-posting: see
http://fedoraproject.org/wiki/Communicate/MailingListGuidelines#replying 

-- 
E-mail:     james@ | Mike Andrews' Corollary to Murphy's Law:
aprilcottage.co.uk | In any sufficiently large collection of texts, every
                   | possible misspeeling, as well as some that are not
                   | possible, will occur.




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