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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.

Boot from iSCSI "Attempt" configuration

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?
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Magic. That's how it works. –  Tom O'Connor Mar 10 at 15:33
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4 Answers

up vote 3 down vote accepted

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).

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Xenserver does seem to support Boot From San. I guess the root of my problem is that I first need to install the OS onto the iSCSI target. I'm going to experiment with that using this procedure prior to beginning the install. –  Zorlack Sep 25 '12 at 20:38
Um, yeah... I think that's what I said. –  Chris S Sep 25 '12 at 20:55
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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.

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I can get the server to boot from a virtual CD fairly easily. But when the server boots there's no sign of an HBA containing a 32GB disk. I was thinking that this might be for two reasons. Either I have a driver issue with the NIC's HBA functionality, or a fundamental misunderstanding of the technology. –  Zorlack Sep 25 '12 at 18:35
That's because the O.S. installer needs to enable and configure its own iSCSI stack after it starts, just like it needs to rely on its own device drivers after a BIOS booted it from a local disk. –  Massimo Sep 25 '12 at 21:32
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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.

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I have been booting off iscsi from my X9DRL for a while now. You need to do a couple of things (one do not update the BIOS unless you absolutely have to, it breaks the configuration, and I spent 3 days trying to figure it out again, ESXi 5.5 needed the BIOS update for myself).

There are 3 steps. 1. Configure the iSCSI settings in the BIOS. 2. Go into the Boot menu, select the hard drive boot priority order, in my case I had 14 disks, and 1 Intel iSCSI (I forget the exact syntax) mount. This is the one you need to select. 3. Change the overall boot order to boot the disk you selected in step 2 to boot first, or in the order that you want it to, CD drive first for example.

I cannot remember if you need to save and reboot after each step... even though I did this last night..

Boot from whatever install medium, and the installer should list the iSCSI drive as one of your install options.

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