Slow resilvering with mirrored ZIL

[Steven Hartland]

----- Original Message ----- 
From: "Freddie Cash" <fjwcash at gmail.com>
>>> I believe -- but I need someone else to chime in here with confirmation,
>>> particularly someone who is familiar with ZFS's internals -- once your
>>> pool is ashift 12, you can do a disk replacement ***without*** having to
>>> do the gnop procedure (because the pool itself is already using ashift
>>> 12).  But again, I need someone to confirm that.
>>>
>>
>> Close, the ashift is a property of the vdev and not the entire pool so
>> if your adding a new vdev to the pool at least one of the devices in
>> said pool needs to report 4k sectors either natively or via the gnop
>>
>    ^^^^^^^^^^^^
> 
> 
>> work around.
>>
> 
> Typo?

This should have read "at least one of the devices your adding as a new vdev
to the pool"

> "... so if you're adding a new vdev to the pool at least one of the devices
> in
> said VDEV needs to report ..."
> 
> I made the mistake of thinking ashift was a property of the pool and added
> 3x 6-drive raidz2 vdevs to an existing pool of 4x 6-drive raidz vdevs
> without using gnop .... and now have 3 vdevs with ashift=9 and 4 vdevs with
> ashift=12.  :(  Here's hoping the box gets replaced before 512b drives are
> discontinued completely ...
> 
> I now have it on my "zpool add" checklist to always use gnop devices,
> regardless of what kind of drive is being used.

If anyone wants my current patches which add switch to 4k ashift by default
as a sysctl + works with QUIRKS too, just let me know.

They are well tested, just we want more options before putting in the tree.

    Regards
    Steve

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