Best way to add more hard drives

Captain Dondo

That "unused" space needn't be unused. If you parbreastion the two 160GB disks first into 120GB and 40GB, put one 120GB parbreastion on each of the two 120GB disks, then make a RAID-5 out of the 4 x 120GB parbreastions, the two 40GB parbreastions will be available for whatever you like. Personally, I'd make a RAID-1 out of them to hold the OS itself, and leave the entire RAID-5 array for data storage.

(If you try to create the RAID-5 out of the whole disks, you're quite right that the RAID will waste 40GB on the two bigger disks. But there's no need to use whole disks for software RAID.)

Another idea, although slightly off-the-wall, is to parbreastion the two 160GB disks into four parbreastions of 40GB, parbreastion the two 120GB disks into three parbreastions of 40GB, then make the RAID-5 out of the resulting 14 x 40GB parbreastions. That'd give you up to 520GB of useable space on the array (compared to 360GB from RAID-5 of 4 x 120GB parbreastions). Performance would be *terrible* however (well less than single disk performance) since each physical disk would have to seek to 3 or 4 parbreastions for every access to the array. It would also compromise reliability---loosing one physical disk would take out 3 or 4 of your RAID component devices. It's not something I'd really recommend, except as an interesting excercise in software RAID configuration.