ZFS cautions (pool flag additions committed)

[Karl Denninger]

On 3/23/2014 2:08 PM, Ondra Knezour wrote:
> Dne 23.3.2014 18:50, Karl Denninger napsal(a):
>> When ZFS code imports are brought forward that add feature flags there
>> is a potential time bomb for existing users in that creation of a new
>> pool becomes non-revertible (except read-only!) with regard to mounting
>> on older revisions of the code.
>>
>> ....
>> The primary "gotcha" here occurs if you don't upgrade your emergency
>> boot media and for some reason you need to boot from a CD or USB key --
>> you can be left SEVERELY screwed, and since -RELEASE is typically not
>> rebuilt when this happens if you don't have a second machine laying
>> around on which you can build a RELEASE image....
>>
>
> Excellent candidate for the /usr/src/UPDATING file?
I think so.

The only reason I caught it immediately is that I'm in the arc.c code 
right now with the fix for the "stalls", and caught the file being 
flagged as revved and thus not automatically updated when I did a "svn 
update ." on /usr/src.

ZFS has been (reasonably) stable on feature-set for a while, but now 
we're seeing more pool-level flags show up and in virtually every case 
once those are turned on you can't shut them back off, which slams a 
door on you in terms of being able to revert if something goes wrong.

-- 
-- Karl
karl at denninger.net


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