long time reader, first time asker :)
I have been reading up a lot on iSCSI and SANs in general and I believe I have been able to answer most of my questions and concerns on the topic, but this one remains:
How do you "backup a SAN?"
What follows is a more or less real-world scenario and my thoughts and questions about it.
Suppose you managed to convince the management of your small (at best medium sized) company to finally provide the funds for a small but proper storage solution, i.e. an iSCSI-based SAN. Suppose it consists of a server with many drives in an enclosure and running OpenFiler, or even an MD3000i (Dell) or MSA2000i (HP), which are, as I understand, the most common entry-level solutions.
The LUNs are exported to a server that needs to store code repositories, documents, images and the like, another server that runs a few databases, another that uses the LUNs as disks for virtualization guests (DomUs in Xen-speak) and yet another server that exports one big LUN containing user's home directories via NFS (this is a pure Linux shop). The advantages are clear, I believe: individual servers don't need a lot of local storage and migration of servers or services gets easier.
But now you need to have a backup solution for all or most of the stored data. How do you do it? Do you run backup software (I like rsnapshot) on each and every server that has data to back up? Where do you put that data? On a dedicated backup server with lots of local storage? Or back in the SAN? What is the "common" solution, if any, for backing up a SAN?
I am looking for best practices and advice from people who have more experience than me running SANs.
Edit: considering that the budget for the SAN is very limited to begin with I guess I am looking for non-proprietary, very general and cheap solutions to the backup question. If such solutions exist, anyway. There will not be any money for tapes or a second, identical SAN array. Should have made that more explicit, sorry.