Solved Create RAID-Z1 pool in degraded mode?

[mikkol]

Can I create a RAID-Z1 pool consisting of five vdevs (each a physical disk) but using four vdevs (each a physical disk) attached and marking one as missing and then later add that one disk to make the pool online instead of degraded?

I'm trying to fit 9 disks into 8 slots, and without a hammer and/or a hacksaw this goes poorly (with them, even more poorly), so my idea is to mark one of the drives missing until I can remove three drives and go on with five.

 

[ralphbsz]

A few years ago (perhaps 6 or 8 years), I tried it, and found no way to do it. The problem is that "zpool add" looks for the characteristics of a real existing disk, for example its size. To implement this ability at the time would have required giving the zpool add command options to tell it what the non-existing disk would be like.

It is possible that in the intervening years, this has become possible.

ZFS is not the only file system (with built-in RAID) that is missing this ability (or was at the time).

 

[mikkol]

A few years ago (perhaps 6 or 8 years), I tried it, and found no way to do it. The problem is that "zpool add" looks for the characteristics of a real existing disk, for example its size. To implement this ability at the time would have required giving the zpool add command options to tell it what the non-existing disk would be like.

It is possible that in the intervening years, this has become possible.

ZFS is not the only file system (with built-in RAID) that is missing this ability (or was at the time).

Thank you for this. I will overcome this with some other solution, such as copying over network.

 

[usdmatt]

Not sure if this solves your problem but the following process has been used several times:

Create a pool with X disks and 1 memory backed md device.
Offline the memory disk after creating the pool so it’s degraded. (You can crate a memory disk of any size but obviously don’t really want to copy any actual data to it)
At some point use replace to replace the missing device with a real disk.

 

[mikkol]

Not sure if this solves your problem but the following process has been used several times:

Create a pool with X disks and 1 memory backed md device.
Offline the memory disk after creating the pool so it’s degraded. (You can crate a memory disk of any size but obviously don’t really want to copy any actual data to it)
At some point use replace to replace the missing device with a real disk.

Thank you for a working solution.