The question to ask is do you really need RAID configuration ? What are the RAID levels one should  use? Hardware- or software-based RAID ?

Hardware RAID though could be faster, it is more expensive and if the RAID card fails, the  RAID volume will go down so it constitutes another point of failures in additional to hard disk failures. Software RAID nowadays is getting more versatile and with modern CPU, the speed gap is closing. In fact, most of the time, the difference in speed is not noticeable. With multi-core CPU, the load constitutes less than a few percentage of total CPU load. In terms of features such as disk hot-swap, auto rebuild on line, auto volume extension and flexible data caching, software RAID is not in anyway inferior to hardware RAID.

If speed is the only concern, then RAID 0 is the one to go as it reads and writes the data in strips across mutliple disks in parallel. In fact, the more number of disks, the faster is the read and write speed. Conversely, chance of total failure of RAID 0 volume will increase as the number of disks increases.

If reliability of data is the top priority, then RAID  1 should be used. As the data is mirrored across pair of disks, if any disk failed, all data is intact and one only needs to replace the faulty disk. Besides the data saftety, it does not offer much gain in data writing and reading. The  main downside is 50% of storage space is wasted and not used for additional data storage.

Obviously, using RAID 1 + RAID 0 or RAID 10 is the best of both worlds. Pairs of disks are  mirrored to form RAID 1 volumes which  in turn are combined to form RAID 0 volumes. In this way, data is protected by mirroring while there is speed gain in reading and writing by  stripping data across multiple mirrored volumes.

The most commonly used RAID array is RAID5. While it offers a greater storage space than RAID 1 and more data safety than RAID 0, its writing speed is slow as it needs time to compute parity data blocks on every write.

So the choice of RAID configuration really depends on the considerations  of speed performance, data safety and cost of storage. In case of doubt, RAID 10 should be the way to go.

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