Hello

My question is pretty simple, and I am almost certain the answer is "no", but just to be sure I wanted to ask.

I did something quite stupid, which is that I have shucked about half of my drives (12TB and 18TB, 13 drives total, single-parity) and didn't really pay attention to the details. I now read somewhere that your parity drive determines the speed of your entire array, which I didn't know, and decided to check the parity drive out. Surprise, surprise, my parity drive is shucked and is one of only two in the array which is 5400RPM in stead of 7200RPM. My other 18TB's that are in the array are 7200RPM and only one 12TB is also 5400RPM. So now my question: is it possible with some special procedure to swap a data drive present in the array with the parity drive, without having to buy another 18TB drive (at full cost, since to be sure that it's 7200RPM it can't be shucked) and without losing data? And would this indeed yield a noticeable performance increase? I'm almost certain that this isn't possible, because that would require two drives to be offline at the same time in a single-parity array. But perhaps I'm missing something, so I thought I'd ask.

I do have a two-bay offline (so should be bit-by-bit) HDD cloning station by the way, perhaps that can help? But I'm not sure how risky this is and I'm not sure how Unraid would respond to not only a missing drive but also a parity drive that has changed ID (serial) at the same time. What do you think? So then I would take out both drives, clone the parity drive to the data drive, put the cloned parity drive in and assign it in place of the original one,  start the array which will say that a drive is missing, stop the array, wipe and insert the old parity drive in place of the original data drive and let it rebuild. Seems mighty risky though and I'm not even sure if it's at all possible, given that the parity drive ID will have changed

Cheers!

Edited February 27, 20242 yr by BlueBull

11 minutes ago, BlueBull said:

parity drive determines the speed of your entire array

When writing to the array, speed will be slower than the slowest disk involved in the write. Might be the parity drive.

https://docs.unraid.net/unraid-os/manual/storage-management/#array-write-modes

 

When reading, speed is determined by the speed of the drive that has the file being read since that is the only disk involved (unless the disk is disabled or missing and so is being emulated by the parity calculation).

 

 

You could New Config without parity then start the array so no disks would be considered the parity disk.

 

Then you could shutdown, clone one of the data disks to the former parity disk.

 

Then another New Config would let you reassign the disks as needed and rebuild parity.

You could clone parity instead of data and then make it rebuild data, but the steps to make that happen are more complicated than you describe, and wouldn't save any time.

Alright, sounds logical indeed, thanks for you reply. In your opinion, how risky is this? What happens if, after the procedure you describe of cloning the data drive, the clone isn't bit-by-bit perfect? Suppose I start the array without parity and with an imperfect clone, would I notice this at all? I assume not, unless I have checksum data or the filesystem has catastrophic damage? And if I would in fact notice it, can I just stop the array again and re-insert the original data drive? Also, I might be able to use something like the unbalance plugin to first make sure the data drive is as empty as I can get it, would that be a good idea? I have enough free space for this

This cloning station is from the well-known and often-used brand StarTech by the way, but I haven't used its cloning function before yet

Edited February 27, 20242 yr by BlueBull

If you can make the to-be parity drive empty with all of its data elsewhere, then you can just New Config with all of the disks as you want them to be assigned, rebuild parity on the new parity (formerly data) disk, and format the new data (formerly parity) disk so it is ready for access.

4 minutes ago, trurl said:

If you can make the to-be parity drive empty with all of its data elsewhere, then you can just New Config with all of the disks as you want them to be assigned, rebuild parity on the new parity (formerly data) disk, and format the new data (formerly parity) disk so it is ready for access.

Ah, that is good news. Well all right, I guess I have my answer, that is by far the cleanest and least risky solution. Thank you very much for your prompt assistance and replies, I truly appreciate it