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From: Oliver Freyermuth <o.freyermuth@googlemail.com>
To: Chris Murphy <lists@colorremedies.com>,
	Remi Gauvin <remi@georgianit.com>
Cc: linux-btrfs <linux-btrfs@vger.kernel.org>,
	Thomas Schneider <74cmonty@gmail.com>
Subject: Re: No files in snapshot
Date: Wed, 4 Sep 2019 22:52:38 +0200	[thread overview]
Message-ID: <a6b8e96a-6b66-be0e-e44d-2b65ab7cb2b9@googlemail.com> (raw)
In-Reply-To: <CAJCQCtSG9W93dWwH7++dBGh94s6UGGbugrW8y17OmycC5wP8kw@mail.gmail.com>

Am 04.09.19 um 21:07 schrieb Chris Murphy:
> On Wed, Sep 4, 2019 at 12:24 PM Remi Gauvin <remi@georgianit.com> wrote:
>>
>> On 2019-09-04 1:36 p.m., Chris Murphy wrote:
>>
>>>>
>>>
>>> I don't really know how snapper works.
>>>
>>> The way 'btrfs subvolume snapshot' works,  you must point it to a
>>> subvolume. It won't snapshot a regular directory and from what you
>>> posted above, there are no subvolumes in /var or /var/lib which means
>>> trying to snapshot /var/lib/ceph/osd/ceph-....  would fail. So maybe
>>> it's failing but snapper doesn't show the error. I'm not really sure.
>>>
>>
>> In this case, his snapshots are all of the root.
>>
>> I don't know how Ceph works, but since we already confirmed that there
>> are no subvolumes under /var, the only other explanation is that
>> /var/lib/ceph/osd/ceph-<n> is a submount
>>
>> What is the the result of running:
>> mount | grep /var
>>
> 
> Yep.
> 
> 

Looking at Thomas' mail on the Ceph-users list:
http://lists.ceph.com/pipermail/ceph-users-ceph.com/2019-August/036679.html
I deduce he is using Ceph with the Bluestore backend, which indeed means that /var/lib/ceph/osd/ceph.<n>
are tmpfs mounts which are completeley ephemeral and are created from LVM metadata of the actual Ceph OSD disks. 

That would of course also explain why they are not part of any btrfs snapshot of / (and that also means there is no need to backup anything). 

  reply	other threads:[~2019-09-04 20:52 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-27  9:33 No files in snapshot Thomas Schneider
2019-08-27 22:24 ` Chris Murphy
2019-08-28 14:45   ` Thomas Schneider
2019-09-04 17:36     ` Chris Murphy
2019-09-04 18:02       ` Remi Gauvin
2019-09-04 19:07         ` Chris Murphy
2019-09-04 20:52           ` Oliver Freyermuth [this message]
2019-09-05  8:50             ` Thomas Schneider
2019-09-05 18:31               ` Oliver Freyermuth
2019-09-04  9:24   ` Thomas Schneider

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