Questions about dual parity and SATA card failure

[David Spivey]

As I have been reading the forums, and considering unRAID, I have seen a couple of posts that gender questions about dual parity. Specifically, with dual parity, someone mentioned that drives cannot be moved from one place to another physically. (I would like confirmation on this, since my current setup allows me to place drives in any available SATA port and they are immediately part of the storage again)

This brings me to a real-world scenario that I have experienced, and questions about how a possible failure might occur. In the past, I have purchased PCIe SATA cards to support more hard drives than those for which my motherboard had ports. In my first SATA adapter purchase, the adapter failed after some time. When I replaced it with a new card of the same model, that also failed after time. Eventually, I decided that the brand / model of PCIe card I was using was failure-prone and untrustworthy. I replaced the card with another brand, and so far have had no further issues.

Now for the actual question. If there were 4 drives on a PCIe SATA card on a dual parity unRAID, and the entire SATA card was replaced with a different brand and model (but the existing drives were reattached to this card), how would this affect the unRAID? Would it rebuild Q drive, or would it consider the entire array invalid?

[JorgeB]

1 minute ago, David Spivey said:

Specifically, with dual parity, someone mentioned that drives cannot be moved from one place to another physically.

 

This is not true, you can change controller or ports at will, what you can't change is the unRAID device assignment order without invalidating parity2.

[David Spivey]

Thank you for the immediate response. This gives me a much better feeling about the entire setup.

I also have other questions.

Can one move to-from dual parity at a moment's notice? For example, if I have dual parity set up, and want to go back to single parity temporarily, can that be done?
If I remove a Q drive, does the RAID automatically act as a single parity?
Do I need to upgrade both parity drives one-at-a-time or simultaneously? For example, if I use 2 4TB parity drives, and want to upgrade to 8TB parity drives (so I can add 8TB drives to the pool), do I need to replace one 4TB parity drive, and allow the RAID to do something before adding the other drive?

[JorgeB]

18 minutes ago, David Spivey said:

Can one move to-from dual parity at a moment's notice? For example, if I have dual parity set up, and want to go back to single parity temporarily, can that be done?

 

Yes, from 2 to 1 is instant, from 1 to 2 you'll need to re-sync parity2

 

19 minutes ago, David Spivey said:

If I remove a Q drive, does the RAID automatically act as a single parity?

 

Yes

 

20 minutes ago, David Spivey said:

Do I need to upgrade both parity drives one-at-a-time or simultaneously?

 

However you prefer, the only requirement is that  both parity disks are the same size or larger than the largest data disk, they can be different sizes.

[David Spivey]

Awesome! Thanks again for your swift replies.

[limetech]

Perfect answers @johnnie.black thank you!