DJohnsonRoseDJohnsonRose Member Posts: 55 ■■□□□□□□□□
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)

    **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

    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

    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

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