RBD image format v1 EOL ...

RBD image format v1 EOL ...

[Jason Dillaman]

For the future Ceph Octopus release, I would like to remove all
remaining support for RBD image format v1 images baring any
substantial pushback.

The image format for new images has been defaulted to the v2 image
format since Infernalis, the v1 format was officially deprecated in
Jewel, and creation of new v1 images was prohibited starting with
Mimic.

The forthcoming Nautilus release will add a new image migration
feature to help provide a low-impact conversion path forward for any
legacy images in a cluster. The ability to migrate existing images off
the v1 image format was the last known pain point that was highlighted
the previous time I suggested removing support.

Please let me know if anyone has any major objections or concerns.

Thanks,
Jason

Re: RBD image format v1 EOL ...

[Gregory Farnum]

On Wed, Feb 13, 2019 at 10:37 AM Jason Dillaman <jdillama@redhat.com> wrote:
>
> For the future Ceph Octopus release, I would like to remove all
> remaining support for RBD image format v1 images baring any
> substantial pushback.
>
> The image format for new images has been defaulted to the v2 image
> format since Infernalis, the v1 format was officially deprecated in
> Jewel, and creation of new v1 images was prohibited starting with
> Mimic.
>
> The forthcoming Nautilus release will add a new image migration
> feature to help provide a low-impact conversion path forward for any
> legacy images in a cluster. The ability to migrate existing images off
> the v1 image format was the last known pain point that was highlighted
> the previous time I suggested removing support.

What is the image migration path? I think if we’re going to strip out
the ability to read data then the conversion process should be
automatic-on-access, if that’s possible...
(Also, it's generally good for things like that to provide more than
one release's worth of upgrade-overlap. Especially since we will
support going straight from Mimic to Octopus.)
-Greg
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Re: RBD image format v1 EOL ...

[Jan Kasprzak]

	Hello,

Jason Dillaman wrote:
: For the future Ceph Octopus release, I would like to remove all
: remaining support for RBD image format v1 images baring any
: substantial pushback.
: 
: The image format for new images has been defaulted to the v2 image
: format since Infernalis, the v1 format was officially deprecated in
: Jewel, and creation of new v1 images was prohibited starting with
: Mimic.
: 
: The forthcoming Nautilus release will add a new image migration
: feature to help provide a low-impact conversion path forward for any
: legacy images in a cluster. The ability to migrate existing images off
: the v1 image format was the last known pain point that was highlighted
: the previous time I suggested removing support.
: 
: Please let me know if anyone has any major objections or concerns.

	If I read the parallel thread about pool migration in ceph-users@
correctly, the ability to migrate to v2 would still require to stop the client
before the "rbd migration prepare" can be executed.

	On my OpenNebula/Ceph cluster, I still have bigger tens of images
in v1 format, so it would induce a moderate pain to figure out which VMs
are using them, how availability-critical they are, and finally to migrate
the images.

	But whatever, I guess I can cope with it :-)

-Yenya

-- 
| Jan "Yenya" Kasprzak <kas at {fi.muni.cz - work | yenya.net - private}> |
| http://www.fi.muni.cz/~kas/                         GPG: 4096R/A45477D5 |
 This is the world we live in: the way to deal with computers is to google
 the symptoms, and hope that you don't have to watch a video. --P. Zaitcev

Re: RBD image format v1 EOL ...

[Mykola Golub]

On Wed, Feb 20, 2019 at 10:22:47AM +0100, Jan Kasprzak wrote:

> 	If I read the parallel thread about pool migration in ceph-users@
> correctly, the ability to migrate to v2 would still require to stop the client
> before the "rbd migration prepare" can be executed.

Note, if even rbd supported live (without any downtime) migration you
would still need to restart the client after the upgrate to a new
librbd with migration support.

So actually you can combine the upgrade with migration:

  upgrade client library
  stop client
  rbd migration prepare
  start client

and eventually:

  rbd migration execute
  rbd migration commit

And it would be interesting to investigate a possibility to replace
"stop/start client" steps with "migrating the VM to another (upgraded)
host" to avoid stopping the VM at all. The trick would be to execute
somehow "rbd migration prepare" after the the sourse VM closes the
image, but before the destination VM opens it.

-- 
Mykola Golub

Re: RBD image format v1 EOL ...

[Mykola Golub]

On Fri, Feb 22, 2019 at 02:43:36PM +0200, koukou73gr wrote:
> On 2019-02-20 17:38, Mykola Golub wrote:
> 
> > Note, if even rbd supported live (without any downtime) migration you
> > would still need to restart the client after the upgrate to a new
> > librbd with migration support.
> > 
> > 
> You could probably get away with executing the client with a new librbd
> version by live migrating the VM to an updated hypervisor.
> 
> At least, this is what I have been doing so far when updating Ceph client
> libraries having zero downtime.

Yes, and this is what I meant when I was writing about investigating a
possiblilty to migrate to the new format with zero downtime by using
VM live migration. If there were a way to execute "rbd migration
prepare $pool/$image" during live VM migration, exactly after the
source VM closes the rbd image but before the destination VM opens it,
it would do the trick (the destination VM would start using the new
format).

Right now I don't know if it is possible at all, because I am not
familiar with VM migration, e.g. I don't know if it opens the image on
the destination before or after it closes it on the source.

-- 
Mykola Golub