Monday, November 19, 2012

DHCP Failover Breaks with Custom Options

I was really itching to try out the new DHCP Failover goodies in Windows Server 2012. I ran into a couple weird issues when trying to configure it- hopefully I can save someone else the trouble.

When I tried to create the partner server relationship and configure failover, I'd get the following error: Configure failover failed. Error: 20010. The specified option does not exist.

We have a few custom scope options defined for our IP phones. Apparently, it won't propagate the custom option configuration during the partner relationship setup- you have to do it manually. I haven't found this step or error message documented anywhere in the context of failover configuration.

Since we only had one custom option, and I knew what it was, I just manually added it. If you don't know which options are custom and need to be copied over, it's not hard to figure out. In the DHCP snap-in on the primary server, right-click the IPv4 container and choose Set Predefined Options, then scroll through values in the Option Name dropdown with the keyboard arrows or mouse wheel until you see the Delete button light up (that'll be a custom value). Hit Edit and copy the values down, then in the same place on the partner server, hit Add and poke in the custom values. If you have lots of custom options, you can use netsh dhcp or PowerShell to get/set the custom option config.

Once the same set of custom options exist on both servers, you can do Configure Failover as normal on the scopes and it should work fine. The values of any custom options defined under the scopes will sync up just fine.

I also had one scope where Configure Failover wasn't an option. I had imported all my scopes from a 2003 DC awhile back, so I'm guessing there was something else corrupted in the scope config- just deleting and recreating the scope fixed the problem (it was on a rarely used network, so no big deal; YMMV).

Hope this helps!

Friday, March 2, 2012

Enabling AHCI/RAID on Windows 8 after installation

UPDATE: MS has recently published a KB article on a simpler way to address this. Thanks to commenter Keymapper for the heads up!

Been playing around with Windows 8 Consumer Preview and Windows 8 Server recently. After installing, I needed to enable RAID mode (Intel ICH9R) on one of the machines that was incorrectly configured for legacy IDE mode (why is this the default BIOS setting Dell?). In Win7, you would just ensure that the Start value for the Intel AHCI/RAID driver is set to 0 in the registry, then flip the switch in the BIOS, and all's well. Under Win8 though, you still end up with the dreaded INACCESSIBLE_BOOT_DEVICE. The answer is simple enough: turns out they've added a new registry key underneath the driver you'll need to tweak: StartOverride. I just deleted the entire key, but if you're paranoid, you can probably just set the named value 0 to "0".

So, the full process:

- Enable the driver you need before changing the RAID mode setting in the BIOS:
(for Intel stuff, the driver name is usually iaStorV or iaStorSV, others may use storahci)
-- Delete the entire StartOverride key (or tweak the value) under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\(DriverNameHere)
- Reboot to BIOS setup
- Enable AHCI or RAID mode
- Profit!

Monday, January 9, 2012

Windows installation fails with missing CD/DVD driver

I was recently upgrading one of our large storage servers to a newer version of Windows and came across a really strange error during setup: "A required CD/DVD drive device driver is missing". This was really odd, since I've installed with no problems to this same class of hardware many times (and even this exact piece of hardware). Even stranger, the error popped up regardless if I was using the real DVD drive in the machine or our KVM's "virtual media" feature (which looks like a USB-connected DVD drive to Windows). After lots of searching and trying various things, I remembered what was different about this machine: it had about 30 storage LUNs on it for all the various disks. Hitting the "Browse..." button in the driver select dialog confirmed the problem- Windows was helpfully automounting all the LUNs and assigning drive letters to them. Since there are more than 26, it ran out of drive letters before getting around to mounting the DVD drive. Setup assumes if it can't find the DVD drive, it must be a driver problem, hence the misleading error message. I always disable automount on our storage servers anyway (since we mount all those storage LUNs under NTFS folders, not drive letters), but you can't do that for setup without altering the boot image. The solution in this case was to hit Shift-F10 from the setup dialog to get a command prompt, then use diskpart to unassign D: from a storage LUN and reassign it to the DVD drive.
list vol
select vol X 
(where X is the volume number in the list with D: assigned)
(removes the drive letter)
select vol Y 
(where Y is the volume number in the list that is your Windows Setup DVD)
assign letter=D
Once the setup DVD has a drive letter, you can close the command prompt and proceed with setup normally.