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Choose Your Own iSCSI Adventure


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#1 sfinktah

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Posted 22 December 2011 - 01:15 AM

Choose Your Own iSCSI Adventure

I wasn't entirely joking when I said earlier, I could write 10 tutorials about iSCSI... there are so many combinations of software and hardware (or virtual hardware) that can be used to achieve the same goal without actually varying the method.

Most of the guides concentrate of the setup of DHCP and TFTP, almost all of them for Windows based solutions, and none for 'DNSMASQ' (which is what I used). If I were to write a real guide, it would somewhat like a "choose your own adventure" book.

The simplest iSCSI setup can be achieved by using a VMware machine as the installation target, patching the e1000 virtual BIOS with a copy of gPXE or iPXE.

If you compile or manually type in a small set of commands, you can set up the network (without using DHCP or TFTP), and point it to an empty iSCSI target, then let it boot to a standard install DVD. It would be fairly trivial for me to build two VMware machines that "just ran" that anyone could run, and would "just work". One would be an iSCSI server, one would be a modified e1000 target. They'd be on preset IPs, but after the install, it would be easy enough to image the iSCSI target to a VHD and move it to a Microsoft iSCSI server.

Erwan's iSCSI Setup Guide was quite decent, the reason I failed was an obscure Microsoft bug that I resolved by making a small modification to the iPXE source code.

The basic iSCSI install guide goes like this:
  • Setup DHCP server to instruct the onboard PXE network boot functionality of your PC to chainload gPXE/iPXE,
  • Setup TFTP server to store a copy of the aforementioned gPXE/iPXE
  • Setup an iSCSI target with an unformatted drive.
  • Instruct gPXE/iPXE to connect to that drive
  • Boot install DVD without resorting to reboot.
#5 can be difficult. A lot of BIOS refuse to automatically progress to DVD boot after a failed PXE boot. It's possible to chainload something like PLOP after the gPXE iSCSI connection is made.

The easier solution (I believe) is to install gPXE to a USB drive, then simply "exit" gPXE and let the BIOS move on to the next medium. For that to work, you need a version that supports your network card, (see rom-o-matic).

If you can achieve the gPXE/iPXE to install DVD transition, then all that remains is a bit of trickery or patching to fix the nasty Microsoft bug... the exact details of the bug and some solutions are in my other post http://reboot.pro/15965/ (I include that link for other parties who may read this in the future).

IMHO, iSCSI booting is something that should only be attempted by people already familiar with PXE booting, but I'm just a snob. :P

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So, if you want to setup iSCSI, just tell me what you use for a DHCP server, and what options you have for a TFTP server, and an iSCSI server. As an example, I run my DHCP from an OpenWRT modded NetGear 3700 WNDR (a.k.a. "a linux router"), with TFTP on there, and on my Netgear RNDP NAS (a.k.a. "a linux NAS").

You can skip all the DHCP and TFTP stuff if you're using VMware, or if you have an especially well supported ("old school") NIC. If it's going to be a VMware project, then it's just a matter of setting up an iSCSI Target (Windows Server 2008 R2, or you can download the OpenFiler VM-in-a-box-thing), and tweaking a .vmx file to include a modified ROM image. :dubbio:

#2 erwan.l

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Posted 22 December 2011 - 05:54 PM

Hi Sfinktah,

Nice sum up.

Extra notes : may be we could list here all possible free and non free iscsi target softwares?
I personally like very much starwind.

Also note that MS also made an iscsi target for w2k3 64 bits (version 3.1).

Last question, I was probably too lazy or too dump but I could not find a compiled version of ipxe (no rom-o-matic equivalent).
Would you mind sharing with me (and others) ?

Cheers,
Erwan

update : some softwares are already listed there : http://fr.wikipedia.org/wiki/ISCSI (i have put the french link as it seems the uk link does not list softwares)

to be noted : they are also some nice and cheap hardware alternative as iscsi targets which I have tried and/or owned like the synology and iomega devices.




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