Why vfs.zfs.min_auto_ashift=9 by default?

[Snufkin]

Noticed vfs.zfs.min_auto_ashift tunable is assigned a value of 9 by default.
Are there any valuable reasons not to have default value equal to 12?
It would've assured proper alignment of advanced 4K format HDDs.

[kenZ71]

Paired up with 32bit hardware no longer being supported I have to agree ashift 9 needs to fade away.

[ms49434]

add or modify vfs.zfs.min_auto_ashift in System > Advanced > sysctl.conf and assign a value of 12 will solve your issue. The value might be reset to a lower ashift, depending on the ashift of your vdevices.

[Snufkin]

add or modify vfs.zfs.min_auto_ashift in System > Advanced > sysctl.conf and assign a value of 12...

Ashift value could even be changed on the fly in remote/local shell or N4F Tools|Execute command WebGUI page immediately before creating ZFS pool. Of course it remains in effect until the next reboot.

My question was about the reasons why the default ashift is still 9 and not 12.
Let's consider two cases when N4F user made mistake:

1. vfs.zfs.min_auto_ashift=9 and 4K advanced format HDD - various tests found in the web show speed drop about 5-20 %,
2. vfs.zfs.min_auto_ashift=12 and regular 512 bytes per sector format HDD - no speed drop (512 x 8 = 4096), may cause more ‘dead’ space with small files (less then 4K).

'Dead' space worst case: 7/8 of 4K sector will be empty if file is smaller than 512, which gives, for example, only 1 TB usable out of 8 TB HDD. Pretty frightening figure, isn't it?
Will we ever be faced with such a case? Definitely won't, even size of empty spreadsheet/text document starts from 7K, and all other types of media are much bigger.

I think it's better to eliminate the possibility to make wrong aligned partitions on advanced format HDD.
And not take into account very unlikely situation when ZFS is filled with an incredible amount of tiny files.

[JoseMR]

So I guess a default predefined sysctl for "vfs.zfs.min_auto_ashift" with value=12 could be set under the WebGUI, I was thinking on this time ago also to enforce use of 12.

EDIT: Better let FreeBSD defaults, and user can create a sysctl entry withing WebGUI wen needed.