Create a backup for your server

go to your ssh client (putty),
and before the ~/html folder execute:

zip -v -r -0 ./html/ -x *.mp4 -x *.mp3 -x *.zip -x *.rar -x *.avi  -x ./html/_db_backups/ -x *.svn -x *.tar -x *.md5 -x *.tar.md5 -x *.exe -x *.img -x *.iso -x *.gz -x *.msi -x ./html/stats/

than move the zip file to your html folder,
make sure you have a .htaccess with:

<ifModule mod_headers.c>
  Header unset Accept-Ranges
  Header set Accept-Ranges bytes

and use aria2download from:
to quickly download the file with as much parts (16) as possible.

7zip alternative:

download p7zip_16.02_x86_linux_bin.tar.bz2 from here and extract just the files from p7zip_16.02/bin/ to your account root (above html folder).
run chmod 0775 * to the files and look into some switches that would be useful..

-ssw : compress shared files
-y : assume Yes on all queries

or tar

tar cvpzf backup.tgz --exclude=/proc --exclude=/lost+found --exclude=/backup.tgz --exclude=/mnt --exclude=/sys /

tar -cvpzf backup.tar.gz --exclude=/backup.tar.gz --one-file-system / 

tar vcfz file.tar.gz folder

tar -cvzf output.tgz folder