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Mirror Drives... is one treated as a master?

  • 26-06-2006 10:22pm
    #1
    fatmander
    Closed Accounts Posts: 117 ✭✭


    I recently installed a mirror on WInxp.

    I am curious as to what happens whenever 1 drive gets a bad cluster and the other doesnt.
    Can anyone tell me what happens?

    Does the controller treat one drive as the main drive and then the second as a mirror, so if the main drive gets a bad cluster how does the second one cope?(does it inherit all bad clusters??)

    Also are there any issues with running chkdsk on a mirror array, are there any switches that should be used?

    Thanks in advance for any help

    P4D930,Intel945GTP, ICH7-r,2x250Sata


Comments

  • #2
    SouperComputer
    Registered Users, Registered Users 2 Posts: 6,949 ✭✭✭SouperComputer


    If its a physical bad sector, the HD should have some in reserve and remap accordingly, unbeknown to the RAID controller. When you run out of spare sectors chances are the mirror will break and you will need to swap out a drive.

    Despite having RAID, if you feel you are having problems, backup any important info before running ANY kind of diagnostics, including chkdsk. No out of the ordinary switches are needed to run it on a RAID array.

    Naturally of course, if its a software error, then it will be duplicated across the array.


  • #3
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 92,385 Mod ✭✭✭✭Capt'n Midnight


    Hardware mirror or software mirror ?

    Hardware mirror - means the OS isn't told what is going on and it all depends on the controller and how it manages bad sectors. IDE drives have spare sectors and remap bad sectors to the spare one on the fly - I'm not sure how you know how many times this has happened transparently in the past.

    Software mirror - the OS is aware of what is going on. Going back to NT there are knudges with standard resource kit utils to setup a software mirror even if it isn't supported by the GUI of plain vanilla os. http://www.sysinternals.com/Information/TipsAndTrivia.html#WksFaultTolerance

    to booot from the shadow of a broken mirror - note rdisk(1)

    [boot loader]
    timeout=30
    default=multi(0)disk(0)rdisk(0)partition(1)\FT_TEST
    [operating systems]
    multi(0)disk(0)rdisk(0)partition(1)\FT_TEST="Original Disk"
    multi(0)disk(0)rdisk(1)partition(1)\FT_TEST="Shadow Disk"


  • #4
    fatmander
    Closed Accounts Posts: 117 ✭✭fatmander


    Thanks for the help lads

    Its a hardware raid controller on intels ICH7-r 945 motherboard.

    This PC will never have more than 10GB of data on it, but the data integrity is paramount.

    I was aware that some older controllers used a single drive as a master and just mirrored to the second drive, I am not aware how Intels(or more modern controllers) work. I was worried that

    1/Scandisk would only check one drive, and it would remap the bad sectors to the good drive(which I now believe it will not- it will work independantly?)
    2/ Scandisk would remap file table errors(FAT) to second drive(which I believe it now will?)

    I think uz have answered the most important question (about bad sectors) as this was my biggest worry

    Many thanks for the help


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