Re: RAID10 - Ensure mirrors aren't on same JBOD

[Michael Evans <mjevans1983@gmail.com>]

On Mon, Apr 26, 2010 at 1:20 PM, Andrew Klaassen <clawsoon@yahoo.com> wrote:
> --- On Mon, 4/26/10, Michael Evans <mjevans1983@gmail.com> wrote:
>
>> Or write your own program to generate mdadm headers on
>> uninitialized devices.  Or if it's just a one time thing,
>> write the headers, stop the array, make sure it says what
>> you want, and then force a resync before writing any data.
>
> So the headers determine which disks mirror which disks?
>
> Does that mean that if I ordered my disks correctly on the --create commandline, I could depend on all of the data being ordered the way that some of the data is?  I.e. if I figured out which two disks were mirroring each other, I would know that they'd always mirror each other as long as I didn't update the array metadata in any way?
>
> Thanks.
>
> Andrew
>
>
>
>
>
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Logically that is a valid assumption.  The meta-data identifies the
devices and describes the device storage layout.  If you pop in any
older metadata devices with a newer kernel and/or version of mdadm the
old layout must still be supported so that the data can be accessed.
Why would anyone want to bother moving already written data without a
reshape command of some kind?
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