Is it ok to have and RAID and nonRAID on the same disk?

[Ramasubramanian Ramesh <rramesh@ti.com>]

I am interested in pariring 2x250G into raid mirror for linux 
installation. However I do not want to use entire 250G into mirror. 
While I believe
it is technically possible to have couple of partitions in raid 1 and 
the rest as plain disk, I am looking for advise as to whether this is 
ok? recommened? or not recommened. I am really looking for exper 
opinions. I plan to have the following

/dev/hdx and /dev/hdy:
   partition1: 8G (ntfs)
   partition2: 8G (ntfs)
   partition3: 150G (ext3)
   partition4: rest (extended)
   partition5: 8G (linux raid /root)
   partition6: 8G (linux raid /usr)
   partition7: 60G (linux raid /home)

I like to combine /dev/hdx5+/dev/hdy5 for /root, /dev/hdx6+/dev/hdy6 for 
/usr and /dev/hdx7+/dev/hdy7 for /home in raid mirrors.
I like to keep /dev/hdx3 and /dev/hdy3 as simple plain data area for 
audio/video etc that does not need as much fault tolerance.
In fact everything here will be in some CD/DVD, so I won't even backup.

Is this a good plan or am I making fundamental mistake in combining non 
raid and raid partitions?

Regards
Ramesh