Yes, 'mv' on the client is just a metadata operation and not what I'm talking about. The idea is to bring the old pool in as a cache layer, then bring the new pool in as a lower layer, then flush/evict the data from the cache and Ceph will move the data to the new pool, but still be able to access it by the old pool name. You then add an overlay so that the new pool name acts the same, then the idea is that you can remove the old pool from the cache and remove the overlay. The only problem is updating cephfs to look at the new pool name for data that it knows is at the old pool name.
The other option is to add a data mover to cephfs so you can do something like `ceph fs mv old_pool new_pool` and it would move all the objects and update the metadata as it performs the data moving. The question is how to do the data movement since the MDS is not in the data path.
Since both pool names act the same with the overlay, the best option sounds like; configure the tiering, add the overlay, then do a `ceph fs migrate old_pool new_pool` which causes the MDS to scan through all the metadata and update all references of 'old_pool' to 'new_pool'. Once that is done and the eviction is done, then you can remove the pool from cephfs and the overlay. That way the OSDs are the one doing the data movement.
I don't know that part of the code, so I can't quickly propose any patches.
----------------
Robert LeBlanc
PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
Robert LeBlanc
PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
On Fri, Jun 28, 2019 at 9:37 AM Marc Roos <M.Roos@xxxxxxxxxxxxxxxxx> wrote:
Afaik is the mv now fast because it is not moving any real data, just
some meta data. Thus a real mv will be slow (only in the case between
different pools) because it copies the data to the new pool and when
successful deletes the old one. This will of course take a lot more
time, but you at least are able to access the cephfs on both locations
during this time and can fix things in your client access.
My problem with mv now is that if you accidentally use it between data
pools, it does not really move data.
-----Original Message-----
From: Robert LeBlanc [mailto:robert@xxxxxxxxxxxxx]
Sent: vrijdag 28 juni 2019 18:30
To: Marc Roos
Cc: ceph-users; jgarcia
Subject: Re: Migrating a cephfs data pool
Given that the MDS knows everything, it seems trivial to add a ceph 'mv'
command to do this. I looked at using tiering to try and do the move,
but I don't know how to tell cephfs that the data is now on the new pool
instead of the old pool name. Since we can't take a long enough downtime
to move hundreds of Terabytes, we need something that can be done
online, and if it has a minute or two of downtime would be okay.
----------------
Robert LeBlanc
PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
On Fri, Jun 28, 2019 at 9:02 AM Marc Roos <M.Roos@xxxxxxxxxxxxxxxxx>
wrote:
1.
change data pool for a folder on the file system:
setfattr -n ceph.dir.layout.pool -v fs_data.ec21 foldername
2.
cp /oldlocation /foldername
Remember that you preferably want to use mv, but this leaves (meta)
data
on the old pool, that is not what you want when you want to delete
that
pool.
3. When everything is copied-removed, you should end up with an
empty
datapool with zero objects.
4. Verify here with others, if you can just remove this one.
I think this is a reliable technique to switch, because you use the
basic cephfs functionality that supposed to work. I prefer that the
ceph
guys implement a mv that does what you expect from it. Now it acts
more
or less like a linking.
-----Original Message-----
From: Jorge Garcia [mailto:jgarcia@xxxxxxxxxxxx]
Sent: vrijdag 28 juni 2019 17:52
To: Marc Roos; ceph-users
Subject: Re: Migrating a cephfs data pool
Are you talking about adding the new data pool to the current
filesystem? Like:
$ ceph fs add_data_pool my_ceph_fs new_ec_pool
I have done that, and now the filesystem shows up as having two
data
pools:
$ ceph fs ls
name: my_ceph_fs, metadata pool: cephfs_meta, data pools:
[cephfs_data new_ec_pool ]
but then I run into two issues:
1. How do I actually copy/move/migrate the data from the old pool
to the
new pool?
2. When I'm done moving the data, how do I get rid of the old data
pool?
I know there's a rm_data_pool option, but I have read on the
mailing
list that you can't remove the original data pool from a cephfs
filesystem.
The other option is to create a whole new cephfs with a new
metadata
pool and the new data pool, but creating multiple filesystems is
still
experimental and not allowed by default...
On 6/28/19 8:28 AM, Marc Roos wrote:
>
> What about adding the new data pool, mounting it and then moving
the
> files? (read copy because move between data pools does not what
you
> expect it do)
>
>
> -----Original Message-----
> From: Jorge Garcia [mailto:jgarcia@xxxxxxxxxxxx]
> Sent: vrijdag 28 juni 2019 17:26
> To: ceph-users
> Subject: *****SPAM***** Migrating a cephfs data pool
>
> This seems to be an issue that gets brought up repeatedly, but I
> haven't seen a definitive answer yet. So, at the risk of
repeating a
> question that has already been asked:
>
> How do you migrate a cephfs data pool to a new data pool? The
obvious
> case would be somebody that has set up a replicated pool for
their
> cephfs data and then wants to convert it to an erasure code pool.
Is
> there a simple way to do this, other than creating a whole new
ceph
> cluster and copying the data using rsync?
>
> Thanks for any clues
>
> Jorge
>
> _______________________________________________
> ceph-users mailing list
> ceph-users@xxxxxxxxxxxxxx
> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>
>
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