You can use kfs or cwfs with venti but the usual combination is venti with fossil, this is more of a symbiotic arrangmenet than venti would be with the others. Cwfs contains an archival server and a short term store like venti and fossil.
mirroring and striping is possible with cwfs's backend, or with the fs server which can run under any filesystem. Erik has some reccomended supermicro dual atom motherboards for a server, I use one but the older model which draws a bit more power for the glue logic. Personally I have one of these dual atom motherboards, two Enterprise duty 500Gb SATA3 drives, from different manufacturers (with the hope that one will fail before the other), and I run fossil +_ venti + a cpu + auth server on this box as my home server. the disks are mirrored partition by partition, This includes a 200Gb as a jutebox partition with ripped iso images of usefull CDROMs. -Steve