[ceph-users] Moving bluestore WAL and DB after bluestore creation

Richard Hesketh richard.hesketh at rd.bbc.co.uk
Wed Nov 15 09:15:25 PST 2017


Has anyone tried just dd-ing a block.db partition from one device to another and updating the symlink in OSD metadata partition? Ceph doesn't have commands that support you moving these partitions from one device to another, but I don't see a technical reason why manually copying these things should fail.

Additionally, you can at least take solace in the fact that Bluestore is far more efficient anyway and so your SSDs will see much less throughput than equivalent filestore journals and therefore last a lot longer.

On 15/11/17 17:07, David Turner wrote:
> I'm not going to lie.  This makes me dislike Bluestore quite a bit.  Using multiple OSDs to an SSD journal allowed for you to monitor the write durability of the SSD and replace it without having to out and re-add all of the OSDs on the device.  Having to now out and backfill back onto the HDDs is awful and would have made a time when I realized that 20 journal SSDs all ran low on writes at the same time nearly impossible to recover from.
> 
> Flushing journals, replacing SSDs, and bringing it all back online was a slick process.  Formatting the HDDs and backfilling back onto the same disks sounds like a big regression.  A process to migrate the WAL and DB onto the HDD and then back off to a new device would be very helpful.  
> 
> On Wed, Nov 15, 2017 at 10:51 AM Mario Giammarco <mgiammarco at gmail.com <mailto:mgiammarco at gmail.com>> wrote:
> 
>     It seems it is not possible. I recreated the OSD
> 
>     2017-11-12 17:44 GMT+01:00 Shawn Edwards <lesser.evil at gmail.com <mailto:lesser.evil at gmail.com>>:
> 
>         I've created some Bluestore OSD with all data (wal, db, and data) all on the same rotating disk.  I would like to now move the wal and db onto an nvme disk.  Is that possible without re-creating the OSD?

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