Questions on adding a drive


aqua

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Looking for some confirmation before I do something wrong:

 

I had an 8TB drive as a parity drive but got a new 10TB drive and put it place of the old drive and parity is now rebuilding. I want to add that old 8TB drive to the array, which should be simple enough, but have a few questions:

1) I assume there is no point in preclearing a drive that was working fine in operation for several months, right?

2) I was thinking I'd like to add the drive and then start making better use of the split levels, and would likely want to reorder my disks as I have some smaller ones ahead of it in the disk order. Is there anything special to do for this? Do I need to add the drive and then move them around in one step, two steps? From what I understand, the "new config" isn't what I'm after (though I am confused as to when it would be used to add multiple disks at a time - wouldn't that destroy parity?) and that I would just stop the array and move drive orders - right?

 

Also, to confirm, drive order is tied to serial number of the drive and not the connector the drive goes to, right? I should be able to move drives to other ports (including expander cards (not the ssd cache though)) anywhere without consequence, right? With dual parity does that change?

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21 minutes ago, aqua said:

1) I assume there is no point in preclearing a drive that was working fine in operation for several months, right?

Right. Probably won’t be necessary.

 

23 minutes ago, aqua said:

2) I was thinking I'd like to add the drive and then start making better use of the split levels, and would likely want to reorder my disks as I have some smaller ones ahead of it in the disk order. Is there anything special to do for this? Do I need to add the drive and then move them around in one step, two steps? From what I understand, the "new config" isn't what I'm after (though I am confused as to when it would be used to add multiple disks at a time - wouldn't that destroy parity?) and that I would just stop the array and move drive orders - right

Maybe I’m missing something but why change the disk order?

 

25 minutes ago, aqua said:

Also, to confirm, drive order is tied to serial number of the drive and not the connector the drive goes to, right? I should be able to move drives to other ports (including expander cards (not the ssd cache though)) anywhere without consequence, right? With dual parity does that change?

UnRAID uses serial number to ID the drives. As long as it sees the SN it will recognize the drive.

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Disk order impacts the order that the allocations will fill up said disks - but maybe it doesn't matter enough to worry about it. I was thinking I would want my largest disks (8TB x2) to be disks 1 and 2 and my 5TB to be disk 3 and my 4TB to be disk 4, but maybe this isn't totally worth dealing with. 

If I choose to do it though, I still want confirmation of how I should be doing it. Thanks.

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If you want to re-order the drives I would add the new drive first and let the clear complete, then do a new configuration and let parity re-build.

 

9 hours ago, aqua said:

Disk order impacts the order that the allocations will fill up said disks

This is only true if you use the allocation method “fill up”. Perhaps it might be easier in the long run to use “high water” which will check to see which disk has the most free space and write to that disk until half of that space has been filled. It will then check again to see which disk has the most free space. I think this allocation method is probably the most used but there are others. Turn on the help menu (? Icon) while on the share setting page will show you a brief description of each.

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High-water Choose the lowest numbered disk with free space still above the current high water mark...

 

The above is from the help - meaning that the fill goes in disk number order, which is why I was thinking I should have my largest drives first, but that might be not really a big deal.

 

I'm still confused as to the whether I would need to use "new configuration" - isn't that just for multiple drive adds or removals? Couldn't I just swap the drive allocations around after stopping the array and then rebuild parity?

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1 hour ago, aqua said:

 

I'm still confused as to the whether I would need to use "new configuration" - isn't that just for multiple drive adds or removals? Couldn't I just swap the drive allocations around after stopping the array and then rebuild parity?

It is also the only way you can re-order drives!     In the special case of only having parity1 (not parity2) you can re-order drives without breaking parity.     You can therefore use the New Config tool, re-arrange the drives into the order you want, and then tick the ‘Parity is Valid’  box before starting the array to commit the new order of drives and the array will start without needing to rebuild parity.

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