more on bogged down server

[Steve Rieger]

> You have to reduce your load somehow.  Ideally, you should create an
> anonymous FTP download directory and move all of the downloadable files
> to it.  The download directory also is used as the home directory for
> the anonymous FTP user (user "ftp").  I actually use a completely
> separate filesystem entirely for that.  The filesystem is mounted so
> that only root has write access.
>
> Modify your vsftpd.conf file to permit anonymous downloads only
> and start up vsftpd.  Make sure you also set the "force chroot for
> anonymous users" option.  Then change your links on your web pages to
> use "ftp://"-style links pointed at the anonymous download directory
> paths for the downloadable files.
>
> FTP is the protocol to use for large file downloads.  HTTP just isn't
> efficient for that, as you've now found out (the hard way, I might add).
>   

as the man said, dont use http for this,

if you must then i suggest that you have a separate partition for your 
large files and make fstab read as such (example)

/dev/web /                       ext3    defaults,directio        1 1

add the directio comment and the file will not go to ram, nor to swap. this will speed up things, but you should hand the downloads over to a different method (not http).