Are there plans to allow VDEV removal from pools that have VDEVs with different ASHIFT values?

[Binarus]

Dear experts,

some time ago I have created several pools that consist of mirror VDEVs with ashift=13 (I did that because the datasheets of the SSDs we used at that time mentioned a page size of 8192 bytes). In the meantime, I have learned that I better should use ashift=12, simply (a) because everybody does it and it is well tested and (b) because datasheets of today's SSDs don't mention physical or flash page sizes at all.

Now these pools run out of space. We already have bought decent SSDs to extend them. Each two of the new SSDs will form a mirror device that will be attached to the current pools.

Now we have two options how to do that; these options differ significantly regarding the time and effort they will take:

1. Make the new VDEVs with ashift=13. That's not the favorite solution due to reasons mentioned above. But on the other hand, all VDEVs in the pool would still have the same ashift value afterwards, which would allow to remove the smaller VDEVs without hassle if further pool expansion is needed and there are not enough HDD / SSD trays left.
2. Make the new VDEVs with ashift=12. That's the favorite solution due the reasons mentioned above, but then the VDEVs in the pools would have different ashift values. Currently, this would prevent VDEV removal and could turn into a problem if the pools must be expanded further and (one of) the current small VDEVs must be removed to to that because there are not enough free trays in the servers.

Of course, it would be best if we could remove VDEVs from pools even if the VDEVs in the pool have different ashift values.

Therefore I would like to know if there are plans to support this. Please note that this is not a "When will this feature be available" question; I really would just like to know if it is being considered at all.

I am quite sure that it will be a year or so until the next pool expansion is necessary. If the feature is considered, I'll take the risk and create mixed-ashift pools for the moment, hoping that the feature will have arrived before I need to remove the smaller VDEVs. If the feature is not considered, I'll now create new pools, copy the current datasets to them and re-configure the servers so that they boot from the new pools (that's quite some work and tests because this are ZFS-on-root installations with dataset encryption).

I hope that somebody from the development team can answer whether the feature is considered :-)

Thank you very much in advance,

Binarus

[amotin]

Instead of removing old vdev of smaller devices I would one by one replace them by bigger ones and let ZFS to expand the vdev. It would be much less traumatic for the pool than vdev removal. Though the vdev will keep its old ashift.

What's about removals with different ashifts I haven't heard about any work in that direction, but I guess it might be possible to remove vdev with bigger ashift, but not with the smaller.

[Binarus]

Thank you very much. That was fast :-)

I'll then take the extra effort now, because I would not like to initialize the new SSDs with ashift=13. The amount of data surely will increase, not decrease, hence copying everything to a new pool in the future will cause more trouble than doing it now.