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Date:      Tue, 14 Oct 2014 13:26:44 +0200
From:      Mark Martinec <Mark.Martinec+freebsd@ijs.si>
To:        freebsd-fs@freebsd.org, freebsd-stable@freebsd.org
Subject:   Re: zpool import hangs when out of space - Was: zfs pool import hangs on [tx->tx_sync_done_cv]
Message-ID:  <543D0874.9080809@ijs.si>
In-Reply-To: <A7771879317F4194A1D5E4921CD33593@multiplay.co.uk>
References:  <54372173.1010100@ijs.si> <644FA8299BF848E599B82D2C2C298EA7@multiplay.co.uk> <54372EBA.1000908@ijs.si> <DE7DD7A94E9B4F1FBB3AFF57EDB47C67@multiplay.co.uk> <543731F3.8090701@ijs.si> <543AE740.7000808@ijs.si> <A5BA41116A7F4B23A9C9E469C4146B99@multiplay.co.uk> <CAHM0Q_N%2BC=3qgUnyDkEugOFcL=J8gBjbTg8v45Vz3uT=e=Fn2g@mail.gmail.com> <6E01BBEDA9984CCDA14F290D26A8E14D@multiplay.co.uk> <CAHM0Q_OpV2sAQQAH6Cj_=yJWAOt8pTPWQ-m45JSiXDpBwT6WTA@mail.gmail.com> <E2E24A91B8B04C2DBBBC7E029A12BD05@multiplay.co.uk> <CAHM0Q_Oeka25-kdSDRC2evS1R8wuQ0_XgbcdZCjS09aXJ9_WWQ@mail.gmail.com> <14ADE02801754E028D9A0EAB4A16527E@multiplay.co.uk> <543C3C47.4010208@ijs.si> <E3C3C359999140B48943A0E1A04F83A9@multiplay.co.uk> <CAHM0Q_O7LNBiQAEjygANa%2B0rqm9cywjTPbNXabB4TePfEHAZsA@mail.gmail.com> <A7771879317F4194A1D5E4921CD33593@multiplay.co.uk>

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On 10/14/2014 10:14, Steven Hartland wrote:

>>> Yer zfs list only shows around 2-3GB used too but zpool list
>>> shows the pool is out of space. Cant rule out an accounting
>>> issue though.
>>
>> 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.
>
> Its not clear but I believe it could just be fragmention even though
> its ashift=9.
>
> I sent the last snapshot to another pool of the same size and it
> resulted in:
> NAME       SIZE  ALLOC   FREE   FRAG  EXPANDSZ    CAP  DEDUP  HEALTH
> ALTROOT
> sys1boot  3.97G  3.97G   190K     0%         -    99%  1.00x  ONLINE  -
> sys1copy  3.97G  3.47G   512M    72%         -    87%  1.00x  ONLINE  -

Yes, that's it! Fragmentation.

> I believe FRAG is 0% as the feature wasn't enabled for the lifetime of
> the pool hence its simply not showing a valid value.

Indeed. The pool has a long lifetime and the feature was only recently
made available.

> zfs list -t all -r sys1boot
> NAME                                  USED  AVAIL  REFER  MOUNTPOINT
> sys1boot                             1.76G  2.08G    11K  /sys1boot
> sys1boot/ROOT                        1.72G  2.08G  1.20G  /sys1boot/ROOT
> sys1boot/ROOT@auto-2014-08-16_04.00     1K      -  1.19G  -
> sys1boot/ROOT@auto-2014-08-17_04.00     1K      -  1.19G  -
> sys1boot/ROOT@auto-2014-08-19_04.00     1K      -  1.19G  -
 > [...]
> sys1boot/ROOT@auto-2014-09-19_22.20     1K      -  1.20G  -
> sys1boot/ROOT@auto-2014-09-19_22.30      0      -  1.20G  -

So snapshots were not consuming much, it was fragmentation.

Thanks!
   Mark




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