One disk member of two Disk arrays

Question

I will start with my question and then make a short example:

Is it a good idea to split a disk into multiple partitions and create different disk Arrays (raid1/raid5) with those paritions? Are there any Problems/risks?

And now the example:

Say I have three disks. Two have the same size and one has twice as much:

Disk a: |---------------|
Disk b: |---------------|
Disk c: |-----------------------------------|

Now I would create the following two disk Arrays

     Array 1           Array 2
|-----Disk a----| |-----Disk b----|
|----Disk c/1---| |----Disk c/2---|

Disk c was split up into two partitions, one Partition is used to create a raid1 with disk a and the other Partition is used to create a raid1 with disk b.

With this Approach, all the disk space is used and nothing is wasted. I know that a failure of disk c will degrade both disk Arrays. Are there any other Problems/risks involved?

Answer 1

The only risk is what you've already identified. This is a common practice on smaller Netapp systems, however the tradeoff is a much increased level of overhead.

edit: to clarify, on Netapp, all disks are divided into the same partitions, and raids are made from those. All the same raid level, all the same disks. In your scenario, as @Chopper3 mentioned, you'll have uneven amounts of work being done on different disks, which is bad.

Answer 2

Is it a good idea

No, and we try very hard to avoid R5 these days too by the way, please don't - stick to R6/60 and 1/10.