Boot from iSCSI. How does it work?

I have a Supermicro 2uTwin2 blade server which we're hoping to run XenServer on.

Because this motherboard only provides Intel's fakeraid, I was hoping to leverage its boot from iSCSI functionality to get some redundancy.

I can't figure out how this is meant to work.

My best guess would be that the NIC acts like an HBA, allowing me to boot off a CD and then install the OS onto the NIC-based disk. However this doesn't seem to be the case.

I can define an iSCSI target in the BIOS, and when the server boots I see it connect momentarily. Then it seems to disconnect and move-on.

So, my questions:

• Can someone explain how the Boot From iSCSI process is meant to work?
• How can I install an OS on to an iSCSI volume?

Solution 1:

Here's what happening:

1. iSoE tries to boot form iSCSI, doesn't find a bootable LUN, disables the HBA functionality (waiting for some other software to configure it).
2. Loads from CD. CD's OS doesn't see the HBA because it hasn't configured the iSoE of the NIC.

What you'll need to do: Boot from the CD, mount the iSCSI LUN (either through software or hardware) then install to that "drive". Then boot via iSCSI and it should be picked up.

Note: You need to use an OS that supports booting from iSCSI. Xen is not an OS, it's just a baremetal hypervisor. So whatever DomU you use must support booting from iSCSI. For Others reading this: I don't know which do offhand, but it should be in their spec list. For Xenserver (this question asked specifically about): Does support booting from iSCSI, the procedure is generally the same as any Linux, but a good writeup can be found here: Booting XenServer 5.5 from iSCSI (I'm not affiliated with this site).

Solution 2:

You said the server is correctly connecting to the iSCSI disk, so the reason it's not booting is simply because... there's no O.S. installed on it; that's the exact same thing that would happen with a local disk when no O.S. had been installed yet.

You need to perform the O.S. installation, exactly as you would do it if the server's disk was a directly-attached one; what exactly you should do depends on the actual server you're using: it could have a physical DVD-ROM unit (maybe shared between various blades), or some remote management adapter you could use to connect an ISO image, or you could do it using PXE if you have a PXE server available.

Solution 3:

You can use flash storage like PEN Drive or SD CARD to put XenServer. You don't need redundancy on Hypervisor.If SD CARD or PEN Drive fails, just replace with another with a backup of HV. When you have xenserver installed, use iSCSI targets to store VMs. If you have XenServer Enterprise and SANs in HCL of citrix, you can use Storage Link to manage volumes of your virtual machines.