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Thread: RAID - Redundant Array of Independent Drives - The Real How To by... Max

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    Post RAID - Redundant Array of Independent Drives - The Real How To by... Max

    So this is the thread that everybody has been asking me about...
    ok here we go... pictures and all... links and all...

    We call ourselves techs but do we care about our data? I remember the days of napster and when my 2.5gb maxtor was full and I was invincible... until it crashed. I realised that I was going crazy . I couldn't sleep well; don't laugh cuz if this happened to me prob a few months ago, you would hear about me in the news.

    On setting out to build my ultimate machine, I decided that raid would have to be an integral part of the infrastucture of the system. I penciled out what the specs should be then started my research. I was so clueless about the topology that I did reading like crazy (read your literature and do your homework). I am now 99% raid compliant.

    So on with the types of raid:

    0 or what we call stripe; increases read and write speeds exponentially ie 2 drives gives 2 x regular speeds, 3 drives gives 3 x regular speeds and so on. This technique has what we call no "fault tolerance" ie if the array is broken, the data is lost. With newer technology though, you realise that a hard drive can give us 3 to 4 years pending cooling is added or operating under extremely cool conditions.

    1 or what we call mirror; increases read speeds exponentially as well but has a little drop in write speeds, nothing significant to even notice. This technique is the first of fault tolerance methods that is available throughout the raiding topology. Data is written to two separate hard drives which must be of the same size or will be of the same size of the smaller drive if one is bigger than the other. Essentially if one drive fails then windows/controller will only report it but continue to use the other. Once replaced windows/controller will rebuild the array and resync the drives.

    JBOD or Just a Bunch Of Disk; otherwise called spanning, this is somewhat of a raid 0 but does not require drives to be the same size. For example a 20 + 80 + 40 would give you one big volume of 140 with no speed improvement and still suffering the same faith of raid 0 if one drive fails.

    5 or Raid with parity; This is basically a raid 0 with parity data written to each disk and a seperate disk which would be used to reconstruct any disk out of the array in case one fails. This raid has fault tolerance

    0+1 or Mirroring of a Stripe; kinda self explanatory; hence the minimum of this array would have to be 4 drives. This raid has fault tolerance.

    Now I have explained the topology and techniques, on to raid in windows.
    Last edited by MaxFactor1; Mar 22, 2005 at 05:56 PM.
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    Default Re: RAID - Redundant Array of Independent Drives - The Real How To by... Max

    You decide which array ur going to use? R u one who just wants SPACE!!! Or u care about ur data... hehhehehe.
    When i setup my next machine i intend to have some fault tolerance for my system.
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    Default Re: RAID - Redundant Array of Independent Drives - The Real How To by... Max

    Quote Originally Posted by MAX
    0 or what we call stripe; increases read and write speeds exponentially ie 2 drives gives 2 x regular speeds, 3 drives gives 3 x regular speeds and so on.
    This is not entirely accurate based on your explanation. Exponentially is when a thing is increased by powers example squares,cubes etc. What you are saying that if you have 3 IDE running as one the transfer rate would be 3 x 150 = 450 or if it was 4, 4 X 150 =600. What you describe was linear increase i.e just changing the multiplier. If it were exponential it would be 150 ^ 2 for 2 IDEs or 150 ^ 3 for 3 drives. You get what i saying now?

    Aside from that, I'm glad that you posted this info. So i take it that RAID O + 1 is the best way but more expensive if you value your data. I prefer RAID 1 with probably two 120GB SATA HDD. That should do it. I value my music and I pray that my HDD doesn't fail me. I may not have as much as you guys but 3000 songs nuff fi me.
    So i guess thats why XP installed in six minutes but with RAID 1 which I would think run 266mb/s SATA, how long would that take? Dont worry...I think i can do the math

    I think it would be around 7 minutes........
    Last edited by Electrotechnic; Mar 22, 2005 at 06:24 PM.

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    Default Re: RAID - Redundant Array of Independent Drives - The Real How To by... Max

    It would be even nicer to build your own NAS using a mini-itx board, linux, and a fiber channel card (come to think about it not sure if fibre channel is for outside the box). it would cost a pretty penny but it would be an awesome storage system.

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    Default Re: RAID - Redundant Array of Independent Drives - The Real How To by... Max

    The RAID levels mentioned are the popular ones, there are RAID's 0 to 6, 10, 50, and 0+1.

    RAID 0 requires a minimum of 2 disks - odd or even amount of disk
    RAID 1 requires a minimum of 2 disks - even amount of disk
    RAID 5 requires a minimum of 3 disks - odd or even amount of disk

    If you have 6 20 GB hard disk:
    RAID 0 = 120 GB, if n-1 disk fails, all data is lost
    RAID 1 = 60 GB, if n/2 + 1 disk fails, all data is lost
    RAID 5 = 100 GB, if 2 disk fails, all data is lost

    N = number of disks.
    Last edited by juba; Mar 22, 2005 at 07:13 PM.

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    Default Re: RAID - Redundant Array of Independent Drives - The Real How To by... Max

    Could I set up 4 hard drives for data and an extra hard drive for parity? Like say all drives are identical, my data is stored on the 4 hard drives like normal C,D,E,F, but the extra drive has parity bits for each 4 bits across C,D,E,F, so if one of the 4 drives fail, it can be recovered form using the parity bit stored on the extra hard drive??? I am lazy to google this.

    In any event, I would use raid with fault tolerance, and not performance. I think.
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    Default Re: RAID - Redundant Array of Independent Drives - The Real How To by... Max

    Quote Originally Posted by birchoff
    It would be even nicer to build your own NAS using a mini-itx board, linux, and a fiber channel card (come to think about it not sure if fibre channel is for outside the box). it would cost a pretty penny but it would be an awesome storage system.
    You correct, a fibre card cost about $900

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    Default Re: RAID - Redundant Array of Independent Drives - The Real How To by... Max

    IDE 0 backed up on IDE 1
    IDE 0 Fails, No Data Is Lost

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    Default Re: RAID - Redundant Array of Independent Drives - The Real How To by... Max

    @juba
    u got a link.
    From max's post, I think Raid 5 only can handle one bad disk, but your's says, data is lost at 5-2=3 bad drive, meaning, it can handle 2 bad drives?

    I will google it later and come back.
    Let's act on what we agree on now, and argue later on what we don't.
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    Default Re: RAID - Redundant Array of Independent Drives - The Real How To by... Max

    Quote Originally Posted by crosswire
    @juba
    u got a link.
    From max's post, I think Raid 5 only can handle one bad disk, but your's says, data is lost at 5-2=3 bad drive, meaning, it can handle 2 bad drives?

    I will google it later and come back.
    With RAID 5, if you lose 1 disk, you are ok, if you lose 2, data is gone, I am 100% sure about that.

    I have edited the post to reflect that.
    Last edited by juba; Mar 22, 2005 at 07:14 PM.

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