Though not available for GNU/Linux, just currently available for Free/Open/NetBSD, you might want to keep an eye on this project. Incase it is ported to GNU/Linux in the future.
Or if you find this project utmost important to you, you can always decide to install FreeBSD. Both these options are free.
Vinum, "The Vinum Volume Manager is a block device driver which implements virtual disk drives. Vinum implements RAID-0 (striping), RAID-1 (mirroring) and RAID-5 (rotated block-interleaved parity). It was inspired by the The VERITAS® volume manager volume manager and maintains many of the concepts of VERITAS®"
more information on Vinum,
http://www.freebsd.org/doc/en_US.ISO...rticles/vinum/
http://www.freebsddiary.org/vinum.php
some
Vinum benchmarks
Another option which is found under FreeBSD, is '
CCD'
"CCD allows taking several identical disks and concatenate them into one logical filesystem."