Re: ZFS deadlock in 14: without ZIL

From: Dimitry Andric <dim_at_FreeBSD.org>
Date: Sat, 19 Aug 2023 10:31:16 UTC 
On 19 Aug 2023, at 09:36, Graham Perrin <grahamperrin@gmail.com> wrote:
> 
> On 19/08/2023 00:03, Mark Millard wrote:
>> I believe the below quoted messages were reports of deadlocks
>> based on after the following 2 MFV being in place in their
>> environments:
>> 
>> Thu, 10 Aug 2023
>> . . .
>>     • git: cd25b0f740f8 - main - zfs: cherry-pick fix from openzfs Martin Matuska
>>     • git: 28d2e3b5dedf - main - zfs: cherry-pick fix from openzfs Martin Matuska
>> 
>> 
>> …
> 
> Both were ZIL-related.
> 
> <https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=271945#c0> no ZIL; I never used the feature.

The ZIL always exists, but it can be stored on a separate device for
performance reasons. See zpoolconcepts(7), the Intent Log section:

     By default, the intent log is allocated from blocks within the main pool.
     However, it might be possible to get better performance using separate
     intent log devices such as NVRAM or a dedicated disk.  For example:
           # zpool create pool sda sdb log sdc

-Dimitry