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BlueGene
Asked: 2009-06-23 12:32:46 +0800 CST

How to remember RAID levels? [duplicate]

  • 772

How do you remember(if you really do :-)) all the different levels and what each level does? Can anyone suggest an easy way to remember?

raid storage

12 Answers

  1. Remember it like this:

    Watercooler RAID

    • 38
  2. Best Answer

    0 - S (stripe)

    1 - M (mirror)

    5 - P (parity)

    10 - MS (mirror + stripe)

    Smart Men Pay MicroSoft

    or

    Silly Men Pay MicroSoft

    • 17

  3. I remember them in order by the number of punches in the face a failure of any particular level equates to:

    RAID 6 - six punches in the face when it fails, because you had two dang parity drives and thought you were really uber safe....until your Adaptec controller said "no arrays detected".

    RAID 5 - five punches in the face when it fails, especially when your Adaptec controller says "no arrays detected"....or a second drive fails during a rebuild.

    RAID 1 - one punch in the face, especially if you were using a hardware controller and thought you could just take a drive out and grab the data easily...because, hey, it's just a mirror, right?

    RAID 0 - zero punches in the face, because you were expecting it and had full backups.

    P.S. I do not work for Adaptec.

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  4. 0 = No Redundancy

    1 = 100% = 100% Redundancy

    10 = 1 and 0 together

    5 = halfway in-between 0 and 10 (0 uses 4/4 disks, 10 uses 2/4 disks, 5 uses 3/4 disks)

    6 = like 5, plus 1 extra disk needed (e. g. 3/5 disks)

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  5. You learn terms you use daily. 0, 1 and 5 become natural, 6 is just 5 with an extra disk. I've never come across 2,3 or 4.

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  6. Well...

    • RAID 0 is not RAID, it's just AID. That's easy enough.
    • RAID 1 is mirroring. There's one mirrored copy of your data.
    • RAID 2 and 3 are byte-level things that are extremely rare and you don't have to worry about or remember
    • RAID 4 is rare; nearly the same category as RAID 2 and 3
    • RAID 5 can work with five disks. Or only 3... 1 and 10 always need an even number of drives
    • RAID 6 is RAID 5 with one more disk for parity
    • RAID 10 is really raid 1+0, or sometimes 0+1 (those are opposites but many vendors get it backwards). All the two-digit RAID levels are easy, since they're literally just the other two numbers added together.
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  7. RAID 0 - Best performance, poor availability, only suitable for temporary files

    RAID 10 - Good performance for twice the price, quick expansions, rebuilds are straight disk-disk copies

    RAID 5+ - Cheap, poor performance for small random writes (4x), 10+ hour expansions, risky rebuilds, not suitable for hypervisors

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  8. From a security aspect:

    • Raid 0 -> Striping because 0 means No backup if a disk fail
    • Raid 1 -> Mirroring because 1 means a backup if a disk fail

    0 -> Bad for security, 1 -> Good for security

    Usually people only have problems to remember what 0 do and what 1 do.
    You also have to remember 5 and may be 6 which is "5 + one(1) more parity information"

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  9. 4 = like 5, but -1 point for possible hot spot problem

    3 = like 5, but -2 points for seeking like a single drive

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  10. People seem to mostly confuse 0 and 1, but it's pretty easy to remember that RAID 0 provides zero help when you lose a disk.

    RAID 10 is really RAID 1+0 (simple math! ;-)

    RAID 2 to 4 aren't really worth remembering although RAID 4 is what NetApp uses.

    Everyone seems to know RAID 5, so you just need to remember that RAID 6 is an extra parity drive. (RAID 6 doesn't really exist, BTW, it's also sometimes called RAID-DP for Dual Parity)

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