zpool import hangs when out of space - Was: zfs pool import hangs on [tx->tx_sync_done_cv]

[Steven Hartland]

----- Original Message ----- 
From: "K. Macy" <kmacy at freebsd.org>


> On Mon, Oct 13, 2014 at 6:24 PM, Mark Martinec
> <Mark.Martinec+freebsd at ijs.si> wrote:
>> On 10/14/2014 03:15, K. Macy wrote:
>>>
>>> What is using the extra space in the pool? Is there an unmounted
>>> dataset or snapshot? Do you know how to easily tell? Unlike txg and
>>> zio processing I don't have the luxury of having just read that part
>>> of the codebase.
>>
>>
>> Most likely the snapshots (regular periodic snapshots).
>> Changes after upgrading an OS can maybe take an additional 50%
>> of space (just guessing). Btw, ashift=12.
>> Still can't see how that would amount to 4 GiB, but it's possible.
>>
> 
> Disconcerting. Is this something that others are likely to hit? Should
> accounting for writes fail with ENOSPC a bit earlier so that we never
> reach a state like this? I.e. non-metadata writes will fail at a lower
> threshold than data or if that is already the case, reduce the
> threshold further.

I thought I remembered seeing some recent changes in this area, but I can't
find them ATM.

Something to raise on the openzfs list.

    Regards
    Steve