(SOLVED) Dual parity array / Moving disks but retaining same order


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Hi all,

 

This question may have been answered already and If so I apologise.

 

If I move disks 5-8 to slots 9-12 (both physically and in the array configuration), will it invalidate my parity (I have 2 parity drives) ? A picture of my array configuration is attached. I could not find the answer in https://wiki.unraid.net/UnRAID_6/Storage_Management or in the forums.

 

Ultimately, I would like to insert 4 additional drives in slots 5-8.

 

Many thanks for your help.

 

Best

OP

 

array.JPG.6b04f9d9a5cd5c962e41d83494cb7e9a.JPG

Edited by Opawesome
Marked as "(SOLVED)"
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1 minute ago, trurl said:

It will invalidate parity2

Hi trurl,

 

Many thanks for your answer. I appreciate it.

 

So I understand that:

  • parity1 will remain valid
  • party2 will become invalid, although all drives would remain in the same order.

Can you please confirm whether my understanding is correct?

 

Many thanks.

 

Best regards,

OP

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7 hours ago, Opawesome said:

Hi trurl,

 

Many thanks for your answer. I appreciate it.

 

So I understand that:

  • parity1 will remain valid
  • party2 will become invalid, although all drives would remain in the same order.

Can you please confirm whether my understanding is correct?

 

Many thanks.

 

Best regards,

OP

Yes,  the calculations for parity2 includes the drive slot number as one of the input variables while that for parity1 does not.

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21 minutes ago, itimpi said:

Yes,  the calculations for parity2 includes the drive order information as one of the input variables

Hi itimpi,

 

Thank you very much. I am indeed well aware of this. This is why I asked if party2 will become invalid, although all drives would remain in the same order.

 

Is moving disks 5-8 to slots 9-12 (both physically and in the array configuration) considered a "change in the order of the drives" ? 

 

Many thanks.

 

Best,

OP

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1 hour ago, Opawesome said:

Is moving disks 5-8 to slots 9-12 (both physically and in the array configuration) considered a "change in the order of the drives" ? 

Physical configuration doesn't matter, but slot assignment is how drive order is determined. Slot 5 is not equal to slot 9. Just because you move a whole block of drives, it's still a different order because slot 5 doesn't contain the same bits as it did before you reassigned it.

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7 hours ago, Opawesome said:

Ultimately, I would like to insert 4 additional drives in slots 5-8.

The way the OP is worded makes me want to clarify that you can't have gaps in your array slot assignments.

 

And yes, what you describe is considered "reordering" from the UnraidOS point of view (especially w.r.t. the parity2 calculation). And like others have said, the physical configuration doesn't matter at all -- you can change where a drive is physically mounted or which SATA/SAS cables/ports to use between boots and the OS will easily cope with it. (Although I wouldn't switch an array drive from being internally mounted to being in an external USB enclosure.)

 

I used to be overly concerned with the ordering of the drives, but I eventually found that it's best to live with leaving the order alone. Although... I have requested a feature to be able to assign nicknames to the drives to make it easier to manage. But if you do choose to reorder, keep in mind that the 'included/excluded' drive selections in the shares do not automatically update to track the change -- you'll have to update those manually.

Edited by DougCube
strike out incorrect info
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21 minutes ago, itimpi said:

Not true.    You can have as many gaps as you want.  Most people prefer not to have gaps but,Unraid does not enforce this.

Oh, good to know. I struck-out the incorrect info from my reply. Thanks.

I might actually use this 'feature' going forward then.

I just have a slight preference to group up drives of the same capacity and manufacturer.

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