Having trouble deciding

It might work with a ReadyNAS Pro 4, but we recommend that you use Hard Drives that are compatible with the ReadyNAS devices. At this time the Western Digital Caviar Black 3TB drive are not compatible.

I would suggest WD RED Series drives these have been engineered specifically to work in NAS devices,
Western Digital WD RED WD30EFRX 3TB
Western Digital WD RED WD20EFRX 2TB
Western Digital WD RED WD10EFRX 1TB
http://wd.com/en/products/products.aspx ... _wd_red_UK

I don't believe the NAS will support your desired RAID configuration, though you could set up two RAID-0 volumes and schedule Frontview backup jobs to copy data from one to the other. In some ways that is better - giving you more protection against accidental deletion/user error.

Of course if you chose to span RAID-0 over multiple drives, any drive failure will result in all files in the volume being lost. An alternative that avoids this problem is to set up two RAID-1 volumes, putting some shares on one volume, the rest on the other. Protection is at least as good as what you have in mind.

zarra - I'm not sure you are really appreciating the advantages of X-Raid2. You first decide the approximate storage space you need - and for now assume 6TB is what you need, not what you want. You can achieve that volume with 4x2TB or 3x3TB drives, and I also recommend the WD Reds. I have 2x1TB WD10EFRX drives (one came with a new NAS and the other was purchased on one of Newegg's weekend sales. The nominal price of the WD20EFRX at Newegg is $160 (with shipping) and the nominal price of the WD30EFRX is $217 (w/ shipping). So the 4x2TB array would cost $640 and the 3x3TB array would cost $651 yet leaves an empty slot for future expansion. (Note: the actual disk space in both examples after overhead and formatting is approximately 5.4TB). X-Raid2 in a four bay environment is essentially expandable Raid5 which uses one drive for redundancy. (With only two drives it is Raid1, still with one drive for redundancy). Your proposed solution of two Raid1 volumes with 4x3TB drives would cost an extra $217 for the same 5.4TB (net) storage space.

Do not mistake the redundancy for a viable backup. A viable backup requires a separate device, be it a separate external drive (or two), another NAS (which is the fastest and easiest but most expensive) or cloud backup. All hard drives can, do and will fail. It is not a question of if, but when. I once had a drive fail suddenly overnight within a month after purchase, yet it twin (part of a two drive array) ran for over three years in 24/7 RAID service winding up at the end as part of a four drive array in the same NAS it started in. It was retired to occasional use and is still serviceable today.

PapaBear wrote:
Your proposed solution of two Raid1 volumes with 4x3TB drives would cost an extra $217 for the same 5.4TB (net) storage space.

I think he actually wanted to create two RAID-0 volumes and mirror them. Not sure why, as that configuration would only protect against a single drive failure. Creating two RAID-1 makes more sense to me.

Though personally I would use XRAID-2 (or RAID-5) (as you are suggesting).