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remembering raid any good tips

Discussion in 'A+' started by sytch4u, Aug 23, 2009.

  1. sytch4u

    sytch4u New Member

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    hello guys i was wondering if anybody has any good tips on remembering the different types of raid. whitch ones do you need to know for the exam?

    mike
     
  2. zebulebu

    zebulebu Terabyte Poster

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    You should probably know RAID 0, 1 and 5 and how/where they are implemented. The other RAID types are not as common - or used in niche markets like SANs - you should know what they are, but nothing like in as much depth as you need to know 0 (stripe), 1 (mirror) and 5 (stripe with parity). of course, I haven't ever seen an A+ syllabus - let alone a recent one, so someone who has studied for it recently can probably tell you what you should study - or you should be able to get the specs from Comptia's site.
     
    Certifications: A few
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  3. soundian

    soundian Gigabyte Poster

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    That pretty much covers it.
     
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  4. binaryjay

    binaryjay New Member

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    I think the OP meant he wanted a mnemonic representation he could learn..

    What about this:
    0 - zero is not a number, and also not a true fault-tolerant RAID. therefore, it's striped.
    1 - the simplist RAID, as one is a simple number.. mirror
    2 - raid 1 but slightly better, uses partity but only 2 disks (same number as raid#)
    5 - complex RAID, 3 disks (5 minus 3 = 2) i.e. you get two thirds of the total HD capacity
    6 - complex+1 RAID, 4 disks, 2 can fail (1 more than raid 5, hence 5+1=6)
    10 = 1 + 0
    50 = 5 + 0
    etc

    it's unfair if A+ tests you on RAID 2,3,4. they are old.
     
  5. MLP

    MLP Kilobyte Poster

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    WIP: 70-680, 70-270, 70-290
  6. Sparky
    Highly Decorated Member Award

    Sparky Zettabyte Poster Moderator

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    RAID 0, 1 and 5 should be enough tbh and you should know the pros\cons of each.
     
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  7. Sparky
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    Sparky Zettabyte Poster Moderator

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    Only if you are using three disks. The mimimum for RAID 5 is three disks so you could use five or six disks and one disks total capacity is used for fault tolerance spread over all the disks in the RAID.
     
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  8. zebulebu

    zebulebu Terabyte Poster

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    That's actually far more complicated than:
    0=stripe
    1=mirror
    5=stripe with parity
     
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  9. sytch4u

    sytch4u New Member

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    thanks a lot guys this info is very much appreciated :D
     
  10. sytch4u

    sytch4u New Member

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    Nice one :)
     
  11. greenbrucelee
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    greenbrucelee Zettabyte Poster

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    yep 0,1,5 for the a+ is sufficient.
     
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  12. wagnerk
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    wagnerk aka kitkatninja Moderator

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    Nice one :)

    -Ken
     
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  13. Obinna Osobalu

    Obinna Osobalu Banned

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    Nice illustration. :D
     
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  14. MLP

    MLP Kilobyte Poster

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    Thanks

    Another method I have used is:
    RAID 0 - As in nil fault tolerance.
    RAID 1 - 1 is a straight, flat line, like a mirror.
    RAID 5 - A bit here, a bit there, a bit for checking
     
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  15. Notes_Bloke

    Notes_Bloke Terabyte Poster

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    Hi sytch4u,

    This site may be of help to you.

    NB
     
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  16. Shinigami

    Shinigami Megabyte Poster

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    I always had a little trouble remembering which one was which between RAID0 and RAID1. I always considered "mirroring" as the simplest type in that you just have multiple disks with a copy of the same data. Thus my mind would attribute the number 0 for it...

    Took some time to convince my brain that it wasn't so :)

    I'd be surprised if they asked about anything else except RAID0, 1 and 5. I now just keep in my mind the fact that striping is RAID0, and the rest comes along naturally (after all, 5 is a larger number of the three, so it has the be the "complicated" one of the lot, right?).

    And yes, as was mentioned, RAID5 could span multiple disks, not just limited to 3. The actual algorithm (XOR) of finding the missing parity is quite facinating. Once you understand it, it makes a lot of sense and can be quite wondrous to think that out of say 8 disks, you could lose one and yet still have all the data right there and usable (although as you increase the number of disks, the parity calculation gets heavier and heavier on the RAID controller CPU).

    Good luck with the exam.
     
    Certifications: MCSE, MCITP, MCDST, MOS, CIW, Comptia
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