Bluestore : how to check where the WAL is stored ?

[Hervé Ballans <herve.ballans@xxxxxxxxxxxxx>]

Hi all,

I'm setting up my Ceph cluster (last release of Luminous) and I'm currently configuring OSD with WAL and DB on NVMe disk.

OSD data are on a SATA disk and Both WAL and DB are on the same partition of the NVMe disk.

After creating partitions on the NVMe (block partitions, without filesystem), I created my first OSD from the admin node :

$ ceph-deploy osd create --debug --bluestore --data /dev/sda --block-db /dev/nvme0n1p1 node-osd0

It works perfectly, but I just want to clarify a point regarding the WAL : I understood that if we specify a --block-db option without a --block-wal, WAL is stored on the same partition than the DB.

OK, I'm sure it's working like that but how can I check now where the wal is really stored ? (as there is no symbolic link block.wal into /var/lib/ceph/osd/ceph-0 [1] ?)
Is there somewhere or a Ceph command where I can check this ?

I just wanted to be sure of my options before starting deployment on my 120 OSDs !

Thanks for your clarifications,

Hervé

[1] # ls -l /var/lib/ceph/osd/ceph-0/
total 48
-rw-r--r-- 1 ceph ceph 465 Aug 16 14:36 activate.monmap
lrwxrwxrwx 1 ceph ceph  93 Aug 16 14:36 block -> /dev/ceph-766bd78c-ed1a-4e27-8b4d-7adc4c4f2f0d/osd-block-98bfb597-009b-4e88-bc5e-dd22587d21fe
lrwxrwxrwx 1 ceph ceph  15 Aug 16 14:36 block.db -> /dev/nvme0n1p1
-rw-r--r-- 1 ceph ceph   2 Aug 16 14:36 bluefs
-rw-r--r-- 1 ceph ceph  37 Aug 16 14:36 ceph_fsid
-rw-r--r-- 1 ceph ceph  37 Aug 16 14:36 fsid
-rw------- 1 ceph ceph  55 Aug 16 14:36 keyring
-rw-r--r-- 1 ceph ceph   8 Aug 16 14:36 kv_backend
-rw-r--r-- 1 ceph ceph  21 Aug 16 14:36 magic
-rw-r--r-- 1 ceph ceph   4 Aug 16 14:36 mkfs_done
-rw-r--r-- 1 ceph ceph  41 Aug 16 14:36 osd_key
-rw-r--r-- 1 ceph ceph   6 Aug 16 14:36 ready
-rw-r--r-- 1 ceph ceph  10 Aug 16 14:36 type
-rw-r--r-- 1 ceph ceph   2 Aug 16 14:36 whoami

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