Windows server 2012 R2 SAN storage connection

You should probably just use a FC SAN; if you have FC Storage already, you can grab an FC Switch and FC HBAs for the host servers; that will be enough to get a simple FC SAN going.

You can use a server to act as a FC-iSCSI gateway; software like Starwind or SanMelody run on Windows; or most Linux distros come with iSCSI Target software.

Handling the SAN IO will depend on whether it's IOps or MBps you're looking for. More IOps requires more CPU usage to process each; both require as much cache and the fastest buses you can find.

GigE is just as fast as FC; but there's more overhead with GigE usually. iSCSI runs on TCP/IP and that adds a lot of overhead. The Ethernet frame is very comparable to the FC frame however; so technologies like ATAoE and HyperSCSI can keep up, with the caveat that a single 4Gbps FC can do a single stream at that speed, and 4 GigE would need 4 connections to saturate the fabric (theoretically; real life is always a little worse).

So you talk about SATA and SAS drives... do you have a FC to SAS controller that you're planning on plugging into a FC-iSCSI Gateway Server, that's then relayed to the Host servers?? That's a lot of overhead and will pretty much kill performance.

If you want to use SAS hardware you can create a SAS SAN cheaper yet (and no FC or iSCSI); drives plug into it, SAS HBA on the servers, and the SAN chops the drives into "LUNs". Products like the HP MSA2000sa will do this. This is more limited than FC or iSCSI; but for simple environments is very cost effective.

After encountering the same problem again, I tried the PowerShell cmdlets for the storage subsystem, and it helped overcome the problem.

All storage cmdlets can be found here: http://technet.microsoft.com/en-us/library/hh848705.aspx

Using Get-VirtualDisk cmdlet, I was able to find out that the virtual disks have a property called IsManualAttach, which is set to true.

Using Set-VirtualDisk cmdlet, I changed this property to false, and all disks are now attaching at boot time without any problems.

There was no way to find it in the user interface, and there was no hints that there can be such a property. The GUI on Server Manager only showed me a yellow triangle beside the virtual disk names, and when you hover your mouse over it, it says "Unknown: Unknown". I feel online documentation is also not mature enough yet, but I'm very happy with the software.