Boot problem if a ZFS log device is missing

[Johan Hendriks]

Maurizio Vairani wrote:
> On 29/08/2013 11.01, Andriy Gapon wrote:
>> on 29/08/2013 11:27 Maurizio Vairani said the following:
>>> I am able to boot the PC without a cache device but not without a 
>>> log device. Why ?
>> The log could potentially contain uncommitted entries.  Without the 
>> log device
>> there is no knowing if it did or did not.  And if it did then the 
>> pool is
>> inconsistent state without the log device and so it can not be imported.
>>
>> The cache is not persistent and so there is nothing needed from it 
>> upon a boot.
>>
> Thank you for the clear and concise reply.
>
> Yesterday I have done some test. If I remove the stick from the USB 
> port, before the shutdown the PC, it  don't crash but continues to 
> works. Then  I am able to reboot the laptop without inserting the 
> stick with a pool that works in degraded mode.
>
> From the end user point of view a PC should always boot, even with a 
> missing ZFS log device.
>
> Regards
> Maurizio
>
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I do not agree with the following.
     From the end user point of view a PC should always boot, even with 
a missing ZFS log device.

I think it should give you a option to import the pool or not import the 
pool!
There could be a situation when you are not sure that the ZIL is 
commited, in that situation it would be handy if you can suspend the 
boot and make sure the ZIL is there when you reboot or import after you 
attached the ZIL.
I would hate it when it corrups my data just because we always import. 
with or without the ZIL.

In your test you remove the ZIL, and when you reboot then it imports 
correctly, as far as my knowledge goes this is ok, because when the pool 
is exported there is no left data in the ZIL, it was not there when we 
exported, so we can import even without the missing ZIL without problem.

regards
Johan