My crazy partition setup

My requirements

When I built this computer back in January, I had carefully considered the RAID storage configuration. My requirements were basically:

• Must dual boot Fedora and some flavour of Windows (unfortunately)
• Fedora must have a redundant /home partition, as it holds my most important data
• Windows must have a fast Media (aka /home) partition for my audio work
• Would also be nice to have redundant OS partitions

The initial plan

So I decided to buy a pair of identical 320GB disks for the OS, a set of three 640GB disks for my media. My new motherboard had 4 SATA ports on an ICH10R controller, and 2 SATA ports on some other SATA controller.

It seemed best to set up a fakeraid RAID5 array across the 3 media disks in the ICH10R controller, and to let the OSs do their own thing on the 2 OS disks.

I split both of the OS disks in half to allow Linux software RAID1 (mirroring) across both of its RAID partitions, which would be mounted as /. The two partitions showed up to Windows as C: and D:. It is not possible to use Windows software RAID (aka Dynamic Disks) on a Windows boot partition so I installed Windows on C: and used D: for Program Files.

I created a RAID5 array across the 3 disks using the ICH10R RAID BIOS. Booting into Windows, it was immediately spotted so I cut the device in half and created drive J: for my media. Sorted – it was fast and worked nicely.

No such luck with Fedora 10 (the latest relkease at the time I built this PC). Anaconda, the Fedora installer, was not able to see the RAID partition – it only saw the three separate disks. Try as I might, I could not get round this. Kind of a showstopper.

Onto plan B

I figured that I could avoid using the ICH10R fakeraid by keeping the disks as 3 separate disks, cutting each in half and using three halves for Linux software RAID, and 3 halves for Windows Dynamic Disks. No such luck – Windows is only able to use a whole disk as a Dynamic Disk, and wasn’t able to share it with Linux. Bugger.

What I ended up with

Given that Windows and Linux cannot share a RAID array, whether it be software or pseudo-hardware, my only choice was to somehow divide up the disks.

The two OS disks were fine as they were; Windows was not using RAID but rather a more manual approach to having two disks (OS on C: and Program Files on D:).

Eventually I decided to give Windows two of the media disks and use them in a RAID0 (striped) Dynamic Disk for performance. This still gives approximately the performance of a 3-disk RAID5 array, but without the redunancy. I get around this by not keeping anything permanently on the RAID0 array. It is only used as a cache/buffer during audio work, and the audio files are primarily stored on my server via the network.

This left just a single disk for Fedora’s /home partition. It doesn’t tick the box of having redunandcy, but thanks to my hourly backup script this is less essential.

This diagram shows my current sub-optimal setup. Click for a bigger version. Windows partitions are in red and Linux in blue.

The future

Since setting up this PC, I happened across a blog post that seems to be the answer to my prayers. It’s a bit hacky, but it’s the only documented way I have seen of getting a dual-boot system to share an ICH10R array.

Next time I can be bothered to reinstall both OSs, I will write about it here.