Interconnectivity with Xsan is usually a pretty straight forward beast. Make sure you can communicate in an unfettered manner on a house network, on a metadata network and on a fibre channel network and you're pretty much good to go. One thing that seems to confuse a lot of people when they're first starting out is how to configure the two ethernets. We're going to go ahead and do two things at once, explain how to configure the interface and show how to automate said configuration from the command line so you can quickly deploy and then subsequently troubleshoot issues that you encounter from the perspective of the Ethernet networks.

Once upon a time there was Fibre Channel Utility. Then there was a System Preference pane. But the command line utility, fibreconfig, is the quickest, most verbose way of obtaining information and setting various parameters for your Apple branded cards.

To get started with fibreconfig, it’s easiest to start with just asking the fibreconfig binary to simply display all the information available on the fibre channel environment. This can be done by using the –l option as follows:

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Sometimes you just need a small SAN for testing... Times when you don’t have fiber channel and you don’t need to provide access to multiple clients, like maybe if you're writing an article for Xsanity on an airplane. Now this volume is not going to be supported (or supportable) by anyone and nor should it be (so don’t use it for real data), but you can use USB and FireWire drives for a small test Xsan…

The problem

We have a large xsan volume of 28 TB. We want to sync this volume every night to another xsan volume of the same size. In the beginning when the volume was smaller rsync did the job. But now with 28 TB rsync is simply to slow to get the job done in one night.

The solution

I've made a script that uses rsync to get a list of all the changes and then use cvcp to actually copy the data. This dramatically improves the speed. I've tested with 145 GB of data. Rsync did it in 70 minutes and the script did it in 40.

While testing with this I noticed that the CPU and fibre could easily handle another cvcp command at the same time. So I changed the script to do just that. After that the script did the same 145 GB in around 20 minutes.

I am doing a sync now every night with an average of three hours. The amount of data is off course different every night. At the most it needs to transfer 1.5 TB. It might take a little bit longer then but it is still done in the morning.

Apple seems to have released a neat little iPhone web app that has handy information about the Xserve. Ever forget which light to navigate to in order to boot in diagnostic mode? Ever forget the difference between a flickering and flashing System Identifier Light? Seems helpful.