Reed Solomon coding based Raid?

I was wondering if there is support for a raid level where one can choose the redundancy level.  Raid 5 allows for one redundant drive, Raid 6 for two, but there's no raid level that would support arbitrary redundancy (even to the point of allowing one to add extra redundancy later on, by simply putting spare drives to immediate use).

I'm just a casual Software Raid user, and have been using Raid 6 for a small 8 TB array for a few years now and I realize that there's quite some CPU overhead involved for such redundancy, but for my purposes speed is not a relevant concern (10 MB/sec is enough).

--John