Why 2 servers

bullypro's picture

Just curious, I'm looking into setting up Xsan to allow two workstations to share one drive. In the Xsan manual it says I need "Two computers running Mac OS X Server v10.5 to act as SAN metadata controllers." Just curious, why do I need two???

MattRK's picture

The primary reason is for redundancy. It's also considered best practice. If you only have one server and it dies, you will lose everything.

That said, depending on what you are doing, you'd probably be fine with just one server. Just don't put anything on the volume you really want to keep. :)

mark raudonis's picture

X-SAN is NOT a trivial install. If you want to have a reliable, stable, and hi performing system, you really should follow best practices. If you choose NOT to, then, as MattRK says,
"just don't put anything on there you really want to keep".

In my opinion, that's the understatement of the year. Over the years there have been plenty of people who think that X-SAN is just a plug and play install. It's NOT! There's more heavy duty IT details behind it than just about any other shared storage system out there. Having said that, if you follow best practices, X-SAN is wonderful. People get in trouble when they think, "Do I really need a back up?" In a word, YES you do. If you don't understand why, or can't afford it, then this solution is NOT for you.

Mark

PS. Don't think you can go to the Apple store and find anyone at the genius bar who can speak knowledgeably about X-SAN! You'll be disappointed!

I definitely agree that Xsan is not easy to setup so that it works trouble free. It's easy to get working, but hard get right.

However, the comment about losing your whole filesystem in the case of failure when using only one metadata controller is not true. If you've backed up your filesystems configuration files you can replace the machine and get up and running again.

I would only suggest going against the best practices if you really, really know why they are there in the first place.