Which one?

[jessica lina]

Hello! Following advice from Digital Dog, I have now a Sonnet 4 drive Fusion, with 1 TB each.
Configuring it in Disk Utility, on Mac, it proposes me to Spare or to Slice.
Which is the best option ?

[John.Murray]

RAID 1 will utilize 2 Drives, the spare will utilize 1 - leaving a drive unused.  Your total capacity will be 1TB.

An alternate would be RAID1+0 (RAID10) which would consist of 2 RAID 1 pairs stacked in a RAID 0 set.  This would give you a total capacity of 2TB, but no spare.  If you are willing to purchase an additional drive to have on hand, this will give you great performance with a fast rebuild time should an individual drive fail

Another alternative would be RAID5, utilizing 3 Drives, giving a capacity of ~1.86 TB with a spare.  The downside to RAID5 is that data is striped across the 3 drives with parity - this parity calculation involves overhead at the controller and will greatly slow down a rebuild should an individual drive fail

[jonathan.lipkin]

I use RAID 5, as it offers the best comprimise between speed and redundancy. Nearly as fast as RAID 0, and no data loss when a drive dies. However, the rebuild does take a little while, and it's a good idea to have a spare (fifth) drive on hand as (at least for my OWC QX2) the enclosure works best when it has all the same make, model, and firmware drive.

[popnfresh]

RAID 1 and RAID 5 (spare) will both give you data redundancy in the case of a drive failure. But RAID 1 will be faster, while RAID 5 will be larger (3TB vs. 2TB) and somewhat slower.