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  1. #1
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    Add drive to existing RAID array?

    If I want to add a new physical drive to an existing 3 drive logical RAID 5 array to increase total capacity, is there a way to do this without disturbing the data on the existing array?
    Its an HP DL380 G5 server with smart array P400.

    Thanks,
    Rod

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    Did a bit more research and discovered that HP have an Array Configuration Utility that supposedly does this and a whole lot more.
    So I downloaded and installed the latest Windows version, but for some reason it does not seem to offer the extend array option like the documentation says it should. The extend option should show if there is an unallocated physical drive on the same controller as the array, or so it says. I have a physical drive mounted, but can't see the extend option.
    I'll keep experimenting I guess. Maybe I need to format the unallocated drive?

    rstew

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    Super Moderator BATcher's Avatar
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    From a position of some ignorance about your specific HP RAID box, I would say that you should format your intended new drive identically to the other three drives. Then it might stand a better chance of being picked up by the Array Configuration Utility.
    BATcher

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    This depends entirely on the system you have. With RAID 5, you should be able to add a 4th disk, but the only way to be sure is to RTFM (read the f*ing manual) for your controller. It will require some sort of rebuild to integrate the new disk.
    Graham Smith
    DataSmith, Delaware
    "For every expert there is an equal and opposite expert.", Arthur C. Clarke (1917 - 2008)

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    Quote Originally Posted by gsmith-plm View Post
    This depends entirely on the system you have. With RAID 5, you should be able to add a 4th disk, but the only way to be sure is to RTFM (read the f*ing manual) for your controller. It will require some sort of rebuild to integrate the new disk.
    Good suggestion! Actually I did RTFM and found that the Array Config Utility is supposed to enable adding a drive. But though it is listed in the ACU, there is no option to add it.
    And when I go to disk management in the OS, it does not show the unallocated drive, though it shows up in Hard Disk Sentinel just fine.
    So it seems like it needs to be initialized, or formatted maybe, but since it does not show up in disk management there does not seem like a way to do either.

    Stumped
    rstew

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    Quote Originally Posted by rstew View Post
    So it seems like it needs to be initialized, or formatted maybe, but since it does not show up in disk management there does not seem like a way to do either.
    There should be both a firmware/controller based configuration utility and some kind of software/web utility that should take care of that. As long as the drive is the same size and type as the others, and there is a spare connection on the controller, it should (note the use of the word should - as in this is an educated wild ass guess) be able to see and configure that new drive as added storage and integrate it into the array.
    Graham Smith
    DataSmith, Delaware
    "For every expert there is an equal and opposite expert.", Arthur C. Clarke (1917 - 2008)

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    I would check to make sure the drive in NOT ALLOCATED. Not formatted, no partition, no logical drive. Just bare neked HDD.

    David

    Just because you don't know where you are going doesn't mean any road will get you there.

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    While it's not impossible in theory, I've never seen such a capability in practice. It's one of the weaknesses of RAID arrays; systematically increasing the capacity of the array by adding drives requires re-striping the entire array. Which is a total reformat, which means you better be prepared for a complete restore from backup.

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    Quote Originally Posted by BHarder View Post
    While it's not impossible in theory, I've never seen such a capability in practice.
    To be fair, I've never done it or seen it done. But manufacturers claim that you can add an additional drive and the system will rebuild on the fly (whatever that means). In the past, I have interpreted that to mean "start the process before you leave for a three day weekend and it should be done when you return."

    Is it really that much different than hot-swapping?
    Graham Smith
    DataSmith, Delaware
    "For every expert there is an equal and opposite expert.", Arthur C. Clarke (1917 - 2008)

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    ...the system will rebuild on the fly (whatever that means)
    This is standard functionality for rebuilding a RAID array after a drive has failed and you have replaced the failed drive with a new one. It happens because the array has lost redundancy. Integrating the new drive back into the array involves reading every file and calculating parity bits that are then written to the new drive.

    There is definitely a connection with the OP question but it's not exactly the same operation.

    The other part of this problem is the Windows NTFS volume found on the array. Standard volumes are not normally re-sizable on the fly; Windows expects to characterize those volumes at boot time and then they don't change. There is a thing called a Dynamic volume that can do this but most volumes aren't Dynamic.

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    Quote Originally Posted by BHarder View Post
    While it's not impossible in theory, I've never seen such a capability in practice. It's one of the weaknesses of RAID arrays; systematically increasing the capacity of the array by adding drives requires re-striping the entire array. Which is a total reformat, which means you better be prepared for a complete restore from backup.
    I am inclined to think that this is not possible to do, even though the ACU manual says it will work. The manual does say that it will take about 15 minutes per GB, or longer to complete! Wow. Not a fast process.
    I am leaning towards installing a second 2 drive array and migrating the original array contents over to it, then deleting the original array (which will delete all contents), then adding the 4th drive and migrating the contents back to the new array. This looks way easier in the long run.

  12. #12
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    rstew
    Have you checked?
    I would check to make sure the drive in NOT ALLOCATED. Not formatted, no partition, no logical drive. Just bare neked HDD.
    David

    Just because you don't know where you are going doesn't mean any road will get you there.

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    You definitely can add an additional disk to a RAID 5 array - I've done it plenty of times.
    Use the RAID utility built-in to the BIOS - accessable at boot - or the utility for Windows. Do not attempt to use Windows Disk Manager, it doesn't know anything about hardware RAID.
    Fire up the RAID utility and view the status of all the disks - post a pic.
    Set the new disk to available / free.
    Add the new disk to the array.

    cheers, Paul

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