Broadcom/Avago/LSI MegaRAID, possible to remove physical disk then rebuild?

dexvx

[H]ard|Gawd
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Aug 14, 2002
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1,273
So I have 8x 4TB drives in RAID6 on a MegaRAID 9261. I'm slowly migrating data to new 8TB drives (basically whenever Best Buy has a sale on their Easy Stores).

Is it possible to remove one 4TB drive from the RAID6, and then rebuild? Rinse and repeat over a one year period until the 4TB array is gone? Obviously I would free up enough space (and then some).
 
Last edited:
Joined
Dec 27, 2016
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Never tried this.. but I would guess, once you have removed the two parity disks, you cannot remove any more, because to get a file off the remaining six drives, the file is effectively striped across all six.You would somehow have to tell the controller to shrink the pool, but it cannot do that becuase it is not filesystem aware; it only knows about blocks, as far as the controller is concerned, all blocks MAY contain good data.
 

Schmeisser

n00b
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Jan 18, 2016
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You can replace disk 1, for example, wait for the rebuild and then proceed with the next one. Repeating this, you will recieve RAID6 array with 8TB drives, but with old usable capacity (cause the controller will be using only half of the capacity of your drives).
I would recommend you create backups and recreate new RAID array with new drives.
 

ND40oz

[H]F Junkie
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Jul 31, 2005
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12,666
Yeah, there is no way to expand your logical drives just by replacing the physical drives, they'll still show the old smaller capacity once they rebuild. Since your 9261 has all of its ports used, there's no way to add additional drives and create a new array unless you get an expander card and use it. You could do that, move 4 of your current 4TB drive onto the expander and keep the original array intact. Than put 4 of the 8TB drives on the expander, create a RAID 5 array which will get you the same amount of space as your current RAID 6 array and migrate the data to it. Then delete the original 8x4TB array, remove the 4TB drives, add in additional 8TB drives and convert your RAID 5 array to RAID 6 and then expand it.
 

mwroobel

Supreme [H]ardness
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Jul 24, 2008
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While the safest (we’ll most supported way at least) would be to make 2 backups of your data, install the new drives and then copy the data over to the new, larger array. The next supported method would be to do as you suggest and just create an additional file system in the unpartitioned space on the newly expanded array.
That being said, if you are looking to be [H] and experiment (with the suggested 2 (Two) backups in place of course, because you of course have the first “RAID is not a backup” backup in place and a second just in case) I found instances of people successfully doing exactly what you are looking to do with RAID1 arrays (in theory the LSI virtual disk type should be the same) here .
 

dexvx

[H]ard|Gawd
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Aug 14, 2002
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Looks like to much of a hassle.

Probably going to just buy a LSI SAS expander and get rid of all the 4TB's at once.
 
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