quickcel's questions

I am looking to purchase a new server to be used for virtualization and am wondering how many physical network cards to get for the machine. Is there a basic rule of thumb saying something like, "1 network card can support the traffic of 4 virtual servers"?

I'm looking to backup my linux server to Amazon S3 using duplicity.

I found a great resource here that helped me get it setup and am using the basic script that was listed there for me and now copied here:

#!/bin/sh
# Export some ENV variables so you don't have to type anything
export AWS_ACCESS_KEY_ID=[your-access-key-id]
export AWS_SECRET_ACCESS_KEY=[your-secret-access-key]
export PASSPHRASE=[your-gpg-passphrase]

GPG_KEY=[your-gpg-key]

# The source of your backup
SOURCE=/

# The destination
# Note that the bucket need not exist
# but does need to be unique amongst all
# Amazon S3 users. So, choose wisely.
DEST=s3+http://[your-bucket-name]/[backup-folder]

duplicity \
    --encrypt-key=${GPG_KEY} \
    --sign-key=${GPG_KEY} \
    --include=/boot \
    --include=/etc \
    --include=/home \
    --include=/root \
    --include=/var/lib/mysql \
    --exclude=/** \
    ${SOURCE} ${DEST}

# Reset the ENV variables. Don't need them sitting around
export AWS_ACCESS_KEY_ID=
export AWS_SECRET_ACCESS_KEY=
export PASSPHRASE=

Does anyone else have experience with duplicity where they can improve this script and/or share best practices to help create a better script?