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Are Raid drives identified by an ID or by physical slot?
What I mean is with the server powered off can I move the drives to different slots and will the Raid controller simply know which drives are which without any reconfiguration. Reason we want to do this is to separate Raid 1+0 drives across the two SAS channels to ensure resilience if one channel fails, the layout being:
4 - disk Raid 10, S=Stripe, M=Mirror, Assume machine is delivered as:
Slot 0 - S1Ma
Slot 1 - S1Mb
Slot 2 - S2Ma
Slot 3 - S2Mb
To ensure resilience we want to change this across both SAS-A and SAS-B channels:
Slot 0 (SAS-A) - S1Ma
Slot 1 (SAS-A) - S2Mb
Slot 8 (SAS-B) - S2Ma
Slot 9 (SAS-B) - S1Mb
That way is either SAS-A or SAS-B fails the array is still functioning.
theflash1932
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February 20th, 2014 09:00
If done while the server is off, the array will not need to be rebuild ... the controller is smart enough to know the drive's place in the array, regardless of the physical slot it is attached to.
If done while the server is on, the disk will become out of sync with the others and will need to be rebuilt into the array.
DELL-Chris H
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February 19th, 2014 05:00
NickC_UK,
The drives, as well as the controller, all have the raid configuration data stored to them. So if say a slot was to fail, if you take that drive and insert it into another slot then the controller will recognize it as a member of the array and rebuild it automatically. Now with adding a disk, it has no raid configuration data on it, so when it is added it goes to a Ready state and waits.
Now if you add a drive to the controller that has configuration data on the drive that doesn't match the controllers expectations is when you get a Foreign Configuration error.
I hope that helps explain how the drives are identified.
NickC_UK
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February 19th, 2014 09:00
So if a drive is moved from one slot to another with the server switched off will the controller detect that it is part of the same array and simply start using it as before or will that require the array to be rebuilt?