It's fine, you don't need to worry about the WAL device, it is automatically created on the nvme if the DB is there. Having a dedicated WAL device would only make sense if for example your data devices are on HDD, your rocksDB on "regular" SSDs and you also have nvme devices. But since you already use nvme for DB you don't need to specify a WAL device.

Here is some problem:

# ceph daemon osd.8 perf dump bluefs
Can't get admin socket path: unable to get conf option admin_socket for osd: b"error parsing 'osd': expected string of the form TYPE.ID, valid types are: auth, mon, osd, mds, mgr, client\n"

I'm on the host, on which is this OSD 8.

I should have mentioned that you need to enter into the container first

cephadm enter --name osd.8

and then

ceph daemon osd.8 perf dump bluefs

Zitat von Jan Marek <jma...@jcu.cz>:

Hello Eugen,

I've tried to specify dedicated WAL device, but I have only
/dev/nvme0n1 , so I cannot write a correct YAML file...

Dne Po, čec 10, 2023 at 09:12:29 CEST napsal Eugen Block:
Yes, because you did *not* specify a dedicated WAL device. This is also
reflected in the OSD metadata:

$ ceph osd metadata 6 | grep dedicated
    "bluefs_dedicated_db": "1",
    "bluefs_dedicated_wal": "0"

Yes, it is exactly, as you wrote.


Only if you had specified a dedicated WAL device you would see it in the lvm
list output, so this is all as expected.
You can check out the perf dump of an OSD to see that it actually writes to
the WAL:

# ceph daemon osd.6 perf dump bluefs | grep wal
        "wal_total_bytes": 0,
        "wal_used_bytes": 0,
        "files_written_wal": 1588,
        "bytes_written_wal": 1090677563392,
        "max_bytes_wal": 0,

Here is some problem:

# ceph daemon osd.8 perf dump bluefs
Can't get admin socket path: unable to get conf option admin_socket for osd: b"error parsing 'osd': expected string of the form TYPE.ID, valid types are: auth, mon, osd, mds, mgr, client\n"

I'm on the host, on which is this OSD 8.

My CEPH version is latest (I hope) quincy: 17.2.6.

Thanks a lot for help.

Sincerely
Jan Marek



Zitat von Jan Marek <jma...@jcu.cz>:

> Hello,
>
> but when I try to list devices config with ceph-volume, I can see
> a DB devices, but no WAL devices:
>
> ceph-volume lvm list
>
> ====== osd.8 =======
>
> [db] /dev/ceph-5aa92e38-077b-48e2-bda6-5b7db7b7701c/osd-db-bfd11468-d109-4f85-9723-75976f51bfb9
>
> block device /dev/ceph-eaf5f0d7-ad50-4009-9ee6-04b8204b5b1a/osd-block-26b1d4b7-2425-4a2f-912b-111cf66a5970
>       block uuid                j4s9lv-wS9n-xg2W-I4Y0-fUSu-Vuvl-9gOB2P
>       cephx lockbox secret
>       cluster fsid              2c565e24-7850-47dc-a751-a6357cbbaf2a
>       cluster name              ceph
>       crush device class
> db device /dev/ceph-5aa92e38-077b-48e2-bda6-5b7db7b7701c/osd-db-bfd11468-d109-4f85-9723-75976f51bfb9
>       db uuid                   d9MZ2r-ImXX-Xod0-TNDS-tqi5-oG5Y-wrXFtW
>       encrypted                 0
>       osd fsid                  26b1d4b7-2425-4a2f-912b-111cf66a5970
>       osd id                    8
>       osdspec affinity          osd_spec_default
>       type                      db
>       vdo                       0
>       devices                   /dev/nvme0n1
>
> [block] /dev/ceph-eaf5f0d7-ad50-4009-9ee6-04b8204b5b1a/osd-block-26b1d4b7-2425-4a2f-912b-111cf66a5970
>
> block device /dev/ceph-eaf5f0d7-ad50-4009-9ee6-04b8204b5b1a/osd-block-26b1d4b7-2425-4a2f-912b-111cf66a5970
>       block uuid                j4s9lv-wS9n-xg2W-I4Y0-fUSu-Vuvl-9gOB2P
>       cephx lockbox secret
>       cluster fsid              2c565e24-7850-47dc-a751-a6357cbbaf2a
>       cluster name              ceph
>       crush device class
> db device /dev/ceph-5aa92e38-077b-48e2-bda6-5b7db7b7701c/osd-db-bfd11468-d109-4f85-9723-75976f51bfb9
>       db uuid                   d9MZ2r-ImXX-Xod0-TNDS-tqi5-oG5Y-wrXFtW
>       encrypted                 0
>       osd fsid                  26b1d4b7-2425-4a2f-912b-111cf66a5970
>       osd id                    8
>       osdspec affinity          osd_spec_default
>       type                      block
>       vdo                       0
>       devices                   /dev/sdi
>
> (part of listing...)
>
> Sincerely
> Jan Marek
>
>
> Dne Po, čec 10, 2023 at 08:10:58 CEST napsal Eugen Block:
> > Hi,
> >
> > if you don't specify a different device for WAL it will be automatically
> > colocated on the same device as the DB. So you're good with this
> > configuration.
> >
> > Regards,
> > Eugen
> >
> >
> > Zitat von Jan Marek <jma...@jcu.cz>:
> >
> > > Hello,
> > >
> > > I've tried to add to CEPH cluster OSD node with a 12 rotational
> > > disks and 1 NVMe. My YAML was this:
> > >
> > > service_type: osd
> > > service_id: osd_spec_default
> > > service_name: osd.osd_spec_default
> > > placement:
> > >   host_pattern: osd8
> > > spec:
> > >   block_db_size: 64G
> > >   data_devices:
> > >     rotational: 1
> > >   db_devices:
> > >     paths:
> > >     - /dev/nvme0n1
> > >   filter_logic: AND
> > >   objectstore: bluestore
> > >
> > > Now I have 12 OSD with DB on NVMe device, but without WAL. How I
> > > can add WAL to this OSD?
> > >
> > > NVMe device still have 128GB free place.
> > >
> > > Thanks a lot.
> > >
> > > Sincerely
> > > Jan Marek
> > > --
> > > Ing. Jan Marek
> > > University of South Bohemia
> > > Academic Computer Centre
> > > Phone: +420389032080
> > > http://www.gnu.org/philosophy/no-word-attachments.cs.html
> >
> >
> > _______________________________________________
> > ceph-users mailing list -- ceph-users@ceph.io
> > To unsubscribe send an email to ceph-users-le...@ceph.io
>
> --
> Ing. Jan Marek
> University of South Bohemia
> Academic Computer Centre
> Phone: +420389032080
> http://www.gnu.org/philosophy/no-word-attachments.cs.html




--
Ing. Jan Marek
University of South Bohemia
Academic Computer Centre
Phone: +420389032080
http://www.gnu.org/philosophy/no-word-attachments.cs.html


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