3 x ZPOOL ATTACH in a short time - integrity confirmed okay, or resilver manually again to be sure?

[Stilez]

This is a case of "check carefuylly and there won't be any problems", and I suspect the answer is "it'll be fine", but I'd like to have it confirmed by someone with a lot of ZFS experience "just in case".

I have a vdev of 3 x 4TB in my pool that I want to upgrade to a vdev of 3 x 8TB. So I issued 3 x "zpool attach" commands to do so, in CLI, and zpool status then confirmed the vdev has 6 disks and is resilvering. In theory, once it finishes resilvering, I can detach the original 3 disks and it'll be done.

My question is this: when I attached the first disk, it started resilvering it, as usual. Then, when I attached the second disk, what I'm **expecting** is that it restarted resilvering both (i.e. the entire vdev) from scratch again, or else continued resilvering the first new disk and started resilvering the second disk, etc.

But the docs say that only one resilver job runs at a time.

So my question is - before I detach the original HDDs, is there any remote chance that the second and third disks missed a bit of resilvering at the start, or something? Or are all 3 going to each be fully resilvered as expected, even though they started at slightly different times and are being resilvered simultaneously?

 

[dlavigne]

But the docs say that only one resilver job runs at a time.

URL?

 

[Stilez]

URL?

man zpool: "Because scrubbing and resilvering are I/O-intensive operations, ZFS only allows one at a time"

- the man page is a bit ambiguous for this scenario. (I meant man page not docs)

It seems to say that only one resilver operation will be executed at a time. But if I add a disk to a mirror, and it starts resilvering, and then (while it's still resilvering) I attach a second disk to the same mirror as well, is that one or two resilver operations in progress, and if it's one operation, does it correctly handle that one disk has already resilvered some GB but the other hasn't resilvered those GB yet? So the 2 disks are resilvering different source data and playing "catch up". Does it handle that correctly? And I've just started 3 not 2 attaches...

 

[dlavigne]

Did you find a definitive answer for this? If not, have you tried asking on the FreeBSD or OpenZFS forums?