Is there a way to limit a disk's size as seen by Unraid?
I'm thinking of buying a larger disk to future-proof my parity, but having a parity drive significantly larger than data drives seems wasteful / unnecessary. I'm mostly worried about impacting the parity check and rebuild times.

 

eg. Suppose I have 3 disks: 20TB + 4 + 4 ... It's rather useless for the array size to be seen as 20TB rather than 4TB and those checks taking 5x longer than if I had 4 + 4 + 4.

Or am I misunderstanding how this will work? Fingers-crossed, maybe Unraid will speed through the last 16TB without significant impact to overall time?

 

Thanks! Apologies if this has been asked before, but I couldn't find a topic with this specific question.

1 hour ago, ericbox said:

maybe Unraid will speed through the last 16TB without significant impact to overall time?

For parity build / checks it won't, for disk rebuilds it'll only read what's necessary. And no, no such solution.

 

Not much of a deal on something done pretty rarely anyway.

4 hours ago, ericbox said:

Or am I misunderstanding how this will work? Fingers-crossed, maybe Unraid will speed through the last 16TB without significant impact to overall time?

 

If the parity disk is 20TB and the array disks are 4TB, when adding the parity drive to the array it will write parity info matching the 4TB of data, and zero the rest of the drive (which will take a couple of days probably). From then on, the parity checks will only take as long as it takes to read the largest disk in the array, 4TB in your case, and will finish when the 4TBs are read (since it already knows the remaining 16TB are zeros).

 

--Edited to strike incorrect info, it will still read the zeroed portion of the parity drive

 

 

Edited November 26, 20232 yr by Michael_P

19 minutes ago, Michael_P said:

From then on, the parity checks will only take as long as it takes to read the largest disk in the array, 4TB in your case, and will finish when the 4TBs are read (since it already knows the remaining 16TB are zeros).

No, parity check will read the whole drive to verify the remaining 16TB are still zeros.

Edited November 26, 20232 yr by Kilrah

Thanks for the confirmation.
Not the answer I would've liked, but I understand it is an edge use case. And, like you mentioned, at least it shouldn't affect when rebuilding any of the individual smaller data disks.

 

I'm not going to bother raising a feature request, but if anybody from the Lime team reads this and thinks it would be useful, go for it!