andy> I'm looking for a way to create a real-time mirror of a NAS. In andy> other words, say I have a 5.5 TB NAS (3ware 16-drive array, andy> RAID-5, 500 GB drives). I want to mirror it in real time to a andy> completely separate 5.5 TB NAS. RSYNCing in the background is andy> not an option. The two NAS boxes need to hold identical data at andy> all times. It is NOT necessary that the data be accessed from andy> both NAS boxes simultaneously. One is simply a backup of the andy> other. How much data loss can you stand? Or more accurately, how much lag in copying data between the arrays can you stand for your Disaster recovery issues? How far apart are the two systems? Is the setup write intensive, or read intensive? Why is rsync not an option? Not upto date enough? *grin* One option might be to use inotify to watch filesystem A and to copy data that changes to filesystem B as quickly as possible. andy> I guess one option might be to use Redhat's Global File System andy> (GFS). Although there seems to be an 8TB limit for a GFS andy> filesystem, which could be an issue down the road. How large are you planning on growing your filesystem? Why can't it be split? What are your assumptions? andy> But would the following approach work: andy> Can I export NAS B as a SAN or ISCSI target, connect the two andy> machines with, say, mryinet cards or 10 GbE TOE cards, mount the andy> NAS B volume on NAS A, and create a RAID-1 mirror of the two andy> volumes? Is this kind of thing done? I guess I'd look into mirroring the underlying disk subsystems and then putting the NAS on top of that. If the NAS box goes down, you can then just fire up NAS on the backup server and continue. Mostly, I don't understand what problem you're trying to solve, so I can't offer good suggestions because the solution changes depending on assumptions. I already assume you don't have tons of money to spend here. *grin* John - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
