Backups / Dump etc

[Anthony Atkielski]

John writes:

J> If you are running FreeBSD 5.x, you get the cool "L" option on
J> dump which will automatically snapshot the mounted filesystems.

What exactly is meant by a "snapshot," and how much extra disk space
does it require when dump runs?  I've seen the warnings when I run dump
on a running multiuser system in 5.x, and I turned on the L option,
since I'm not hurting on disk space, but I do wonder how much space it
requires (I can't imagine a snapshot that doesn't require a lot of disk
space).

-- 
Anthony