Maybe this has been mentioned before, but it is SO obvious. XRaid needs to support multiple disk sizes (and actually use the space).
For the average home user, nobody wants to make a single purchase of 4 x 2TB drives to replace all their 1 TB drives! The user should be able to purchase a single 2TB drive and replace the smallest drive in the system, increasing overall space - AS NEEDED.
Yes, I'm aware that RAID specifications are based on all drives being the same capacity, but XRaid is already a proprietary extension, right?
Technically, you should be able to use the largest drive for parity, and use the sum of the smallest 3 drives for usable space.
In the FAQ, the example is given of 1x 250G drive and 3x 750G drives. Total usable space is 750G (3x 250G and 250G parity). Doesn't it seem obvious that the space should be 1750G? (250G + 2x 750G and 750G parity). If the user then purchased a 2TB drive, he could replace the 250G and end up with 2250G space (3x 750G and 2TB parity).
When you get this feature completed, I'll be lining up to buy one.
X-RAID2 (found on x86 ReadyNAS e.g. NVX, Ultra, Pro) already will expand when redundant space can be added. See X-RAID2 in Action
When drive bays are full with equal capacity disks you need to replace two disks (replacing one is not enough to add redundant space) to expand a single-redundant volume or if you use dual-redundancy (available on 6-bay or greater ReadyNAS) you'll need to replace four disks with higher capacity disks to expand your volume (see X-RAID2 dual-redundancy expansion paths)
Yes, the Ultra 4 is a great choice. x86 ReadyNAS use fast Intel CPUs. Sparc ReadyNAS (such as the Duo or NV+), have slow Infrant Sparc CPUs. An Ultra 4 would be 2-3x as fast as a Duo or NV+. Also using the Intel CPUs means a much greater range of add-ons can be installed. One other important consideration is that x86 models support 3TB drives whereas the Sparc ones don't and almost certainly never will. An Ultra 4 is a much more future proof purchase than a Duo or NV+.
