How does UNRAID handle file writes while data rebuilding?

[NLS]

To be honest, I have already tried to ignore possible risks in the yearS I use UNRAID and use my server more or less normally.
BUT I would like to have some expert (or official) feedback on how UNRAID handles a file write (or many files write), while data are rebuilding on a disk.

And before people saying that writing usually involves the cache, because it is not always the case... (a) people without cache, (b) shares that are "no cache", (c) file deletes (that also affect the contents of the disk).

More specifically, how does it handle writing:
- to a functional HD in disk blocks that the data rebuild has already passed over.
- to a functional HD in disk blocks that the data rebuild hasn't yet passed over.
- to the emulated (and data reconstructing) HD in disk blocks that the data rebuild has already passed over.

- to the emulated (and data reconstructing) HD in disk blocks that the data rebuild hasn't yet passed over.

 

...and the rare case that the filesystem tries to use blocks on functional or emulated HD... DURING the passing of the rebuild from those very disk blocks.

I want to assume that UNRAID handles all those cases gracefully somehow. But is it the case or someone plays with fire when writing to an array while rebuilding?

 

Edited October 1, 2022 by NLS

[itimpi]

If the rebuild process has passed the point for the sector then both the drive and parity are updated accordingly.   If the rebuild has not reached that point then parity is update parity to apply the change later.    From a user perspective the system acts all the time as though you were writing to the disk in a normal manner.  The only downside to writing to the array while is a rebuild is in progress is that both the write and the rebuild adversely affect each others performance while they are running at the same time.

[BRiT]

3 hours ago, NLS said:

I want to assume that UNRAID handles all those cases gracefully somehow.

It does.

[NLS]

I edited my OP just to add an "S" to "year" (that I use UNRAID).
I suspect 1 year vs 15+ (with a break in between) must be different.

(including how much noob, people consider you when replying )

 

Edited October 1, 2022 by NLS