On 1/2/19 10:43 pm, Alfredo Deza wrote:
>>> I think mounting tmpfs for something that should be persistent is highly
>>> dangerous.  Is there some flag I should be using when creating the
>>> BlueStore OSD to avoid that issue?
>>
>> The tmpfs setup is expected. All persistent data for bluestore OSDs
>> setup with LVM are stored in LVM metadata. The LVM/udev handler for
>> bluestore volumes create these tmpfs filesystems on the fly and populate
>> them with the information from the metadata.
> That is mostly what happens. There isn't a dependency on UDEV anymore
> (yay), but the reason why files are mounted on tmpfs
> is because *bluestore* spits them out on activation, this makes the
> path fully ephemeral (a great thing!)
> 
> The step-by-step is documented in this summary section of  'activate'
> http://docs.ceph.com/docs/master/ceph-volume/lvm/activate/#summary
> 
> Filestore doesn't have any of these capabilities and it is why it does
> have an actual existing path (vs. tmpfs), and the files come from the
> data partition that
> gets mounted.
> 

Well, for whatever reason, ceph-osd isn't calling the activate script
before it starts up.

It is worth noting that the systems I'm using do not use systemd out of
simplicity.  I might need to write an init script to do that.  It wasn't
clear last weekend what commands I needed to run to activate a BlueStore
OSD.

For now though, sounds like tarring up the data directory, unmounting
the tmpfs then unpacking the tar is a good-enough work-around.  That's
what I've done for my second node (now I know of the problem) and so it
should survive a reboot now.

The only other two steps were to ensure `lvm` was marked to start at
boot (so it would bring up all the volume groups) and that there was a
UDEV rule in place to set the ownership on the LVM VGs for Ceph.
-- 
Stuart Longland (aka Redhatter, VK4MSL)

I haven't lost my mind...
  ...it's backed up on a tape somewhere.

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