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RAID Help

DJohnsonRoseDJohnsonRose Member Posts: 55 ■■□□□□□□□□
in Server+
Can someone explain to me what RAID 2,3 & 4 are please? I have tried using CBT nuggets and online materials but i can't seem to get my head round it? Also can someone explain to me the difference between RAID 10 & RAID 1+0/0+1, I have looked on iSCSI RAID Switch, External SATA RAID, vmWare Storage-NAS Network and SAN Data Storage Solutions with JetStor but it looks the same asides from the blocks being copied in a different order. What difference does it offer when you measure the I/O or throughput?Any help would be greatly appreciated as I am taking this exam next week!Thanks in advance guys
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    jibbajabbajibbajabba Member Posts: 4,317 ■■■■■■■■□□
    Raid 1+0 / 0+1 is explained a bit better here.

    Raid 2 / 3 / 4 is a explained a bit better here and here.

    Main difference in certain Raid levels is how data is striped - it can be BLOCK based or BIT based ... easy to miss (the difference that is), which might make it confusing at first.

    I have never taken this exam, but I am working in IT for 15 years now and I never came across a Raid 2, 3 or 4 impolementation :)

    Edit: forgot I DID take Server+ as an early beta .... lol
    My own knowledge base made public: http://open902.com :p
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    DJohnsonRoseDJohnsonRose Member Posts: 55 ■■□□□□□□□□
    Thankyou! I understand RAID 01 & 10 now!!! RAID 2,3,4,6 are a bit more tricky, did you need to learn this for your server +?Do you know where I can take a practice test?
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    DJohnsonRoseDJohnsonRose Member Posts: 55 ■■□□□□□□□□
    So whats the difference between a bit and block? I am aware that 8 bits make a byte but where does a block come into this? Also what's the advantages/disadvantages of striping data at the block level and bit level??
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    EV42TMANEV42TMAN Member Posts: 256
    granted i don't know how much the test is going to cover RAID but in the real world you'll be using 0,1,5,6,10 and maybe 50,60 if in a enterprise. if i remember correctly raid 5 pretty much made 2-4 useless.
    Current Certification Exam: ???
    Future Certifications: CCNP Route Switch, CCNA Datacenter, random vendor training.
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    doverdover Member Posts: 184 ■■■■□□□□□□
    Here's some info I used while studying for the CISSP.

    I typed all this info and then ran across this site - quick and dirty RAID info: Basic RAID Organizations

    RAID-0 Striping
    No redundancy
    Stripes across all disks in an array using all available drive space
    Maximizes space and improves read/write performance

    RAID-1 Mirroring
    Duplicates data from one disk (or set of disks) to another disk (or set)

    RAID-2
    **Requires 39 disks - 32 disks for data, 7 disks for error-recovery code
    RAID 2 system would normally have as many data disks as the word size of the computer, typically 32
    With 32 data disks, a RAID 2 system would require 7 additional disks for ECC
    Data is interleaved at a bit level and can withstand losing 4 error-recovery drives without affecting data

    RAID-3 and RAID-4
    Data striped across a variable number of drivesHas a dedicated parity drivethat can be used to reconstruct data from any single crashed data driveRAID 3 utilizes byte level parityRAID 4 utilizes block level parity

    RAID-5
    Stripes data and parity calculations at the block level across all drives
    Parity information is interleaved
    Disk reads and writes are performed concurrently
    No dedicated parity drive

    RAID-6
    Extends RAID 5 by adding a second parity block distributed across member disksYour array can lose two drives without data loss - protecting against data loss during a rebuild of a failed driveThere is a performance hit for write operations as two parity operations are written across the array

    RAID-7
    Identical to RAID 5 but array functions as a single virtual disk in hardware
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