When should I use the different levels of RAID?

RAID information RAID levels defined Do RAID levels still matter? How to calculate available disk space on a RAID 5

• 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.

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RELATED CONTENT Frequently asked questions RAID is 20 years old. Is it as applicable today as it once was? With a shift toward solid-state disk and semiconductor memory-based storage, does that diminish the need for RAID to boost performance? With the advancements in RAID and storage systems, how come RAID still isn't a replacement for backup? Can you explain what dual parity, distributed parity and network RAID are, and why are they getting more and more attention? How can RAID be used to address green IT issues, and power and cooling challenges in the data center? What are the performance issues with RAID 6 or dual-parity schemes? Is RAID only relevant for the enterprise, or should SMBs and SOHOs be concerned with RAID? Where is the best place and best technique for implementing RAID? It seems like 'hybrid' drives will be here long before true 'solid-state' drives. How do hybrid drives play into RAID schemes and tactics? What's happening with disk rebuild times? How do 'preemptive rebuilds' work, and what other techniques are appearing, if any, to accelerate rebuild times?

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