RAID Help!! - Redhat

This is a discussion on RAID Help!! - Redhat ; 1. How does one recover from software RAID (mirroring). Meaning .. if the primary drive that the PC boots from fails, how do you tell it to automatically boot from the secondary drive. Assume that I am using adaptec scsi ...

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Thread: RAID Help!!

  1. RAID Help!!

    1. How does one recover from software RAID (mirroring). Meaning .. if
    the primary drive that the PC boots from fails, how do you tell it to
    automatically boot from the secondary drive. Assume that I am using
    adaptec scsi and the boot drive is ID 0 and secondary mirror drive is ID 1.

    2. Any one know of any good external rackable 1U SCSI->RAID enclosures
    that has good value and is reliable and is not too pricey? With
    controllers included please..

  2. Re: RAID Help!!

    On Wed, 12 Jan 2005 03:41:45 -0500, Deke wrote:

    > 1. How does one recover from software RAID (mirroring). Meaning .. if
    > the primary drive that the PC boots from fails, how do you tell it to
    > automatically boot from the secondary drive. Assume that I am using
    > adaptec scsi and the boot drive is ID 0 and secondary mirror drive is ID
    > 1.


    This is controlled using the bootloader, either GRUB or LILO.

    Look at the "/etc/grub.conf" file:

    title Fedora Core (2.6.9-1.724_FC3)
    root (hd0,5)
    kernel /vmlinuz-2.6.9-1.724_FC3 ro root=LABEL=/
    initrd /initrd-2.6.9-1.724_FC3.img

    The "root=FOO" tells the kernel where to find the root filesystem.

    HTH.


  3. Re: RAID Help!!

    Deke wrote:
    > 1. How does one recover from software RAID (mirroring). Meaning .. if
    > the primary drive that the PC boots from fails, how do you tell it to
    > automatically boot from the secondary drive. Assume that I am using
    > adaptec scsi and the boot drive is ID 0 and secondary mirror drive is ID 1.
    >
    > 2. Any one know of any good external rackable 1U SCSI->RAID enclosures
    > that has good value and is reliable and is not too pricey? With
    > controllers included please..

    IF you really had RAID 0 - mirroring going, just unplug the bad drive.
    If it does not boot, you didn't have Raid 0 working. For Hardware
    Raid you need to set a new drive in & config.
    There is also a difference if it was Hardware Raid or software raid.
    I had RH using software raid .... lots of other problems it created
    not relating to raid.

    Kahn

  4. Re: RAID Help!!

    frank schrieb:
    > Deke wrote:
    >
    >> 1. How does one recover from software RAID (mirroring). Meaning .. if
    >> the primary drive that the PC boots from fails, how do you tell it to
    >> automatically boot from the secondary drive. Assume that I am using
    >> adaptec scsi and the boot drive is ID 0 and secondary mirror drive is
    >> ID 1.
    >>
    >> 2. Any one know of any good external rackable 1U SCSI->RAID enclosures
    >> that has good value and is reliable and is not too pricey? With
    >> controllers included please..

    >
    > IF you really had RAID 0 - mirroring going, just unplug the bad drive.
    > If it does not boot, you didn't have Raid 0 working. For Hardware
    > Raid you need to set a new drive in & config.


    Just to be correct: the RAID level for mirroring is RAID 1. RAID 0 is
    striping which means that if one drive of the stripe set fails you loose
    all your data on that stripe set.

    > There is also a difference if it was Hardware Raid or software raid.


    Thats correct, but if Deke would have a hardware RAID he would have
    gotten an error message but his system would be still useable/bootable.
    So I assume he's using a software RAID. Ideally (if he has configured
    his system using disk labels) he just has to unplug the broken disk to
    get his system back to life-without the RAID on the boot device. In the
    second step he should edit his grub.conf to change the boot device from
    /dev/sda to /dev/sdb power down the system, put in the replacement for
    the defective disk, reboot, partition and configure the new disk to act
    as mirror for /dev/sdb. The driver should the recognize the
    inconsistency of the RAID and start a rebuild of the mirror.

    HTH

    Andre
    --
    Andre von Raison

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