It’s like a salespitch really.. when your target is a woman, you start talking about the nice color and interior, when the target is a man, you start about the power of the engine. So if you want to sell to a couple, then you must find the perfect balance so both can agree with you.

RAID1 – Regarding, “the replication slows down data transfers”: not true. Writes should be nearly (if not exactly ) simultaneous, as the data should be written to the separate drives at the same time. Read speeds should be improved, since data can come from whatever disk.

RAID5 – Regarding, “you will lose about 30% of the NAS capacity”:  also not true. Unusuable disk space is equal to one hard drive. With 3 drives, 33% is lost; with 4 drives, 25%; and with 5 drives (one of Synology’s other boxes perhaps), 20% is lost.

RAID5+1 – Regarding, “You don’t lose performance under heavy load”: the hot spare does nothing for performance one way or another; this just minimizes the time to rebuild. Speaking of performance and rebuilding, rebuilding storage can take hours, and your array is vulnerable before it’s done. Should another disk fail, your data is toast. Also, write performance is diminished since parity must be calculated.

RAID6  - Almost entirely wrong. While the concept is similar to RAID 5, write performance is slower since two parities must be calculated. This is NOT a mix of RAID 0 and RAID 1. This is usually used when one has a lot of drives in an array (10-12 or more), which would have a greater statistical likelihood of multiple drive failure. It would take 3 drives failing before data is lost. Unusable disk space is two hard drives. With 4 bays, there is no difference in unusable disk space between RAID 6 and RAID 10.

RAID10 – The only RAID description (RAID 0 isn’t real RAID) that is mostly right. Read and write performance is the best out of all the RAID setups. The catch is that it cannot be grown (increased in size); should the user wish to increase storage space, an entirely new array must be built.