re[2]: [linux-lvm] Max storage size per system

[Greg Freemyer <freemyer NorcrossGroup com>]

 >>  2 rotating parity disks ? Can you elaborate on how that works ?
 >>  I have thought about using something else than raid5, where you would
 >>  split the data across a number of disks, AND use a mirrored device for
 >>  storing the parity on.

I don't think it is the same as the above, but on Compaq ProLiants, they have Advanced Data Guard.

http://h18004.www1.hp.com/products/servers/proliantstorage/arraycontrollers/adg/

With it you define the number of data drives(D) you want, and the number of parity drives(P).

Obviously you need D + P drives, but no data is lost until you loose P+1 drives.

The negative is even worse performance than RAID 5, but it does make for greater reliability.

BTW: HP's (Compaq's) "low-end" FC array (MSA 1000) also support Advanced Data Guard.  IIRC their mid-tier and high-end lines don't. 

Greg