A quick note about Openfiler (and I hear NexentaStor is the same) when used as an iSCSI target - you are almost guaranteed to see timeout errors and targets dropping offline, requiring a reboot of the server to correct. This usually happens under heavy load (though I've seen it happen under light loads, too).
We went through hell with Openfiler using iSCSI for several weeks while we tried to nail down the problem. The issue isn't really Openfiler itself, but the iSCSI module it uses (EIT). There was some talk about them converting to SCST, which doesn't have the problem, but so far not a whole lot has happened. A Google search for "Openfiler cmd_abort" will tell you all about the current problems.
What we ended up doing is dumping iSCSI and just using NFS with Openfiler, and everything has been fine since - but since you mentioned iSCSI, I thought I'd mention the problem before you built everything and last had nothing but problems.
Also, Openfiler's management interface has a couple of interesting bugs. We had continuous issues managing large volumes (4Tb), with the interface not letting us delete volumes, or not letting us recreate them after we finally managed to delete them. It appeared that the interface wasn't always cleaning up after itself, leaving things behind. When we later tried to work with the volume, these left behind bits would result in an error behind the scenes when the script issued new commands to the OS, and the web interface would simply refuse to do what it was asked to do (and it didn't report the error it was experiencing when issuing the commands, so you have no idea why it's not working).
In another experience, we wandered into the NIC setup to look at bonding interfaces. We walked through the setup for it, just to take a look, then clicked cancel - Openfiler applied the changes anyway, disconnecting us from the server in the process. We had to jump to the server's console and log in locally, then edit configuration files by hand to regain access to the server.
All in all, not a great experience with Openfiler - and with the project being virtually abandoned since 2009, I'd be inclined to avoid it, or be prepared to fight with it to get it set up, then not touch it for fear of breaking something and losing your data.