ZFS: Is 'zpool add' really irreversible?

Jeremy Faulkner gldisater at gmail.com
Mon Jun 13 12:47:55 UTC 2016

On 2016-06-12 6:50 PM, Matthew Seaman wrote:
> On 12/06/2016 18:14, Yuri wrote:
>> On 06/12/2016 14:58, Brandon J. Wandersee wrote:
>>> `zpool add` adds*virtual*  devices to a*pool*, while `zfs attach` adds
>>> physical devices to a mirrored device. So individual disks can be added
>>> to and removed from mirrored virtual devices, but virtual devices cannot
>>> be removed from a pool.
>> Thank you for your answer. I see that ZFS is designed this way.
>> But I can't say I like this part of ZFS design. Because this isn't a
>> physical disk with the set size, but a combination of disks. People may
>> reasonably want to remove some disks in some layouts, due to failures,
>> etc, and ZFS just lacks the flexibility to do that.
> You should have seen Matt Ahren's talk at BSDCan this year.  (It might
> be available on YouTube in the next few days -- depends if it was
> livestreamed or not.  Unfortunately, while there were lecture 4 tracks,
> there was only one set of video kit to livestream with...)
> Suffice it to say though that there is already fix for those 'Oh No! I
> really didn't mean to type "zfs add" there' moments in the upstream
> OpenZFS repo, which will be coming to a FreeBSD repository near you Real
> Soon Now.  You get a grace period within which you can undo that sort of
> mistake.
> 	Cheers,
> 	Matthew

It appears that multiple days of videos got merged as there are talks 
from the devsummit merged with talks from day one of BSDCan. Here's 
Matt's talk:


Jeremy Faulkner

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