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up vote 7 down vote favorite
4

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?

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10  
Cramming for an exam? Better ace it, because real professionals need to know RAID levels by heart. :) – Boden Jun 22 '09 at 20:39
You do it by understanding of what each level is and does. Anything else is just phony. – poige Mar 16 at 15:32

12 Answers

up vote 10 down vote accepted

0 - S (stripe)

1 - M (mirror)

5 - P (parity)

10 - MS (mirror + stripe)

Smart Men Pay MicroSoft

or

Silly Men Pay MicroSoft

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0 = Stripe = Scary – Tom O'Connor Dec 7 '11 at 22:23
up vote 31 down vote

Remember it like this:

Watercooler RAID

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up vote 11 down vote

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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1  
Hands up everybody who's never cloned a fresh install by yoinking one of the hot-swap disks in a mirror. :) – MikeyB Jun 22 '09 at 21:20
I have heard of backups done with that technique. Works great until the drive you're mirroring off dies, the array decides that the drive that you just added is the new primary, and all your data leaps a week into the past... – RainyRat Jun 22 '09 at 22:03
Second Drive Fails during a rebuild... Been there, would have prefered the five punches to the face! – BillN Jun 22 '09 at 23:15
Hands up everybody who's pulled the wrong drive from a RAID1 array and reformatted the good drive thinking it was the bad one... oh, that'll be my ISP on their mail server :) – gbjbaanb Jan 5 '10 at 23:21
up vote 5 down vote

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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up vote 3 down vote

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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4 is actually used by NetApps. They avoid the hot spot problem with a big battery backed cache – freiheit Jun 22 '09 at 20:48
up vote 1 down vote

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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up vote 1 down vote

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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0+1 and 1+0 are not the same thing, although they are very similar. en.wikipedia.org/wiki/Nested_RAID_levels – Boden Jun 22 '09 at 20:58
yes, 0+1 and 1+0 are opposites (edited to reflect that), sort of. Many vendors get it backwards especially when they just say "10" instead of "1+0" or "0+1", and the actual on-disk layout of blocks is the same, just logically perpendicular. And I've seen setups where creating a 0+1 array still gives you the fault tolerance of 1+0 – freiheit Jun 22 '09 at 21:10
FYI - RAID 3 is is used by EMC for the Cache Vault in their Clariion SAN arrays so it's not really true to say its never used, but it is rare. While there isn't really any performance difference between RAID 10 as 1+0 or 0_+1 there is a big performance difference between RAID 50 meaning a mirror of stripe sets and RAID 50 meaning a stripe of mirror pairs. A stripe of mirror pairs can recover from single drive failures quickly, a mirror of stripes is a lot more work to repair. – Helvick Jun 22 '09 at 21:31
up vote 0 down vote

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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up vote 0 down vote

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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up vote 0 down vote

There is no easy way to remember it. One method i can suggest is as below Raid 0(zero means nothing) so no raid: raid with striping and no redundancy Raid 1(is the first level): so mirroring Raid 5: is striping for fast access and parity for redundancy Raid 6: striping plus double parity Raid 10: raid 1 group in striping http://www.slashroot.in/raid-levels-raid0-raid1-raid10-raid5-raid6-complete-tutorial

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up vote 0 down vote

I like the way: "it is what you get when your disk fails".

RAID 1 = all

RAID 0 = nothing

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up vote -1 down vote

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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