Ubuntu – How to Get Server Hardware Details for Ubuntu Server

Virtual servers take advantage of the fact that most servers do not run at capacity for any length of time, and cpu cycles / memory can be shared. Therefore, it REALLY depends on how busy your virtual machines are.

It also depends on which virtual environment you are using, as to how well it can share memory. (I seem to recall that when I experimented with XEN there was no memory sharing at all - but I think that has now changed).

A development environment is a perfect place to get your feet wet with a virtual environment, and it's real handy to be able to "create a new server" in about 5 minutes if it is needed (even allowing you to over-allocate your resources temporarily in a pinch).

By way of example, we can host approximately 100 virtual machines using VMWare Infrastructure on 5 physical servers. Each of these physical machines has 4 dual core Xeon 2.6Ghz CPUs, 16Gb Ram, and 8 - Gigabit nics. (so an average of 20 VMs on each of these). We find our biggest limitation to be the amount of available memory.

I can say that having worked in a virtual environment for several years now, I wouldn't want to go back.

Hope this helps.

I would use rsync as it means that if it is interrupted for any reason, then you can restart it easily with very little cost. And being rsync, it can even restart part way through a large file. As others mention, it can exclude files easily. The simplest way to preserve most things is to use the -a flag – ‘archive.’ So:

rsync -a source dest

Although UID/GID and symlinks are preserved by -a (see -lpgo), your question implies you might want a full copy of the filesystem information; and -a doesn't include hard-links, extended attributes, or ACLs (on Linux) or the above nor resource forks (on OS X.) Thus, for a robust copy of a filesystem, you'll need to include those flags:

rsync -aHAX source dest # Linux
rsync -aHE source dest  # OS X

The default cp will start again, though the -u flag will "copy only when the SOURCE file is newer than the destination file or when the destination file is missing". And the -a (archive) flag will be recursive, not recopy files if you have to restart and preserve permissions. So:

cp -au source dest