How do server backups (either to tape or disk) work for servers that are running? If you have a large server that needs backing up, wouldn't it take a really long time to back up everything, in which time things could have changed? How do backups deal with consistency?
Of course you could shut down the server every night and then back up, but this doesn't seem like a very efficient way of doing things (you'd be offline daily), and I'm sure isn't what most systems do.
How can you get servers to back up while online, and how does it deal with consistency issues?
Most people run backups during times of low activity (where there aren't files being changed very much). We do an rsync nightly on all systems and haven't had a problem with this.
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How do programs like Amanda back up a server's files while running -- how does it handle the fact that changes are being made while it is doing the backup? (Don't need all the technical details, but just a quick overview of how it does it...the Amanda documentation just confused me...)
It seems like if there were no catch to it, then why doesn't everyone use programs like Amanda to always be able to back up a running server (as opposed to having to temporarily disable their server)?
Also, does rsync handle backups of a running server?
Some software actually has modules for backing up open files. I am not all too familiar with Amanda, but there are a few good backup software out there that will backup open files and running databases.