2 Hard Drives.One Partition

Solution 1:

You can use LVM (see also this guide) or RAID for this. If you want all the space in both drives to correspond to a single partition, LVM is the way to go. You can make an LVM volume group containing both drives, and create a single partition on that.

Since you would want to install Ubuntu on an LVM rather than add an LVM to an already-installed Ubuntu system, you can use the Ubuntu installer to create the LVM, then install Ubuntu on it. The GRUB2 boot loader is fully capable of booting directly into an LVM, so you don't even need a separate /boot partition (as was the old way).

The regular Ubuntu desktop CD (i.e., the live CD) does not have the ability to install Ubuntu on an LVM. Instead, you must use the alternate CD for this. See the "Text-based installation" section on this page. Or, for your convenience:

• This is the 32-bit alternate install CD for Ubuntu 12.04 LTS.
• This is the 64-bit alternate install CD for Ubuntu 12.04 LTS.

Write this .iso image to a USB flash drive, or burn it to a CD/DVD, the same way you would with the live CD.

The official Ubuntu 12.04 LTS installation guide for the alternate CD may help you during the installation process. (Or skip to the 32-bit installation guide or 64-bit installation guide.)

That guide is not very specific about LVM so I'll try to edit this post again to provide detailed instructions, based on your specific needs (an Ubuntu system installed in a single / partition on an LVM consisting of two drives of unequal storage capacity).

Solution 2:

By using RAID. As Eliah Kagan explained in his answer, But keep this in mind:

Ideally you should use two identical hard drives for Raid 1 mirroring. The reason is that both drives will be doing the exact same thing at the exact same time. When you write to one, you’re writing to the other, creating a mirror image of the first. That means both drives will be under the same stress.

Keep in mind too that Raid 1 mirroring will slow your computer because it has to write everything twice. That’s why I recommend the external storage. Put one hard drive in your PC, back it up, and save your data externally.

Back in the days of parallel ATA, it was a no-no to mix drives from different vendors on a RAID controller. Sometimes it would work--more often it wouldn't. With the advent of SATA, mixing vendors is no longer as problematic.

Also, though there are controllers that allow mixing and matching capacities without losing storage space (using advanced parity techniques), these are still relatively rare. Using drives of different sizes usually results in total storage capacity that's only a multiple of the smallest drive. For example, combining 500GB and 320GB drives in RAID 1 would be 320GB * 2, or 640GB instead of 820GB.

In practice, you'll save yourself a lot of time and sidestep possible issues by building your array with identical hard drives--meaning drives of the same make, model, and size. You need at least two drives for RAID 0 and 1, three drives for RAID 5, and four for RAID 0+1, 1+0, and 10.

Hope that this helps in making your decision.

Source: pcworld