When should I use the different levels of RAID?

Here's a synopsis of the different RAID levels as well as when to use each one.

First and foremost, RAID can be used to enhance availability, but it also can be used to enhance performance for I/O, for throughput and things like that. So real quickly. . . . 

  • RAID 0: data spread across multiple drives, gives you performance but no availability;
  • RAID 1: data mirroring. Mirroring data across two or more disk drives gives you availability and can also enhance read operation;
  • RAID 01 or RAID 10: combine striping and mirroring or mirroring and striping for a compromise of good performance and good availability;
  • RAID 3: striping with dedicated parity. Good for large sequential bandwidth operations but not as good for concurrent access.
  • This is where RAID 5 steps in, which stripes the data across multiple drives with rotating parity. This gives you a nice balance of good read performance and reduced cost, because you don't need to have as many drives for mirroring. It's a compromise between performance and availability at the expense of writes, because you have parity updates.
  • Now, you are starting to see dual-parity schemes, such as RAID 6 -- multiple drives striped together with at least two parity drives.

Check out the entire RAID FAQ guide.

This was first published in November 2007

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