Anyone tried RAID6? Can one promote an array from RAID5 to 6?

[Liam Proven]

My Ubuntu server has a RAID5 of 4 40GB IDE disks. I've had to replace
2 failed drives now, so I'm thinking maybe I'll bung in 2 more and
make it a RAID6, so I have 2 spares rather than just 1. That will max
out all the drive connectors in my server - 2 channels on the
motherboard, 2 on an add-in controller.

Currently, there are 5 40s in there - plus a 2G boot drive and a CD-ROM.

It would be handy to set up a RAID5 with the 5 that are in there, then
add in the spare when it arrives from eBay and promote the array from
level 5 to level 6, but I can't find any mention of how to do this on
Google, so I fear it may be impossible.

Comments?

-- 
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