What ceph-disk does when creating a bluestore OSD

Running ceph-disk prepare ...

# ceph-disk prepare --bluestore /dev/sdb
Creating new GPT entries.
The operation has completed successfully.
The operation has completed successfully.
The operation has completed successfully.
meta-data=/dev/sdb1              isize=2048   agcount=4, agsize=6400 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=0, sparse=0
data     =                       bsize=4096   blocks=25600, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
log      =internal log           bsize=4096   blocks=864, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
Warning: The kernel is still using the old partition table.
The new table will be used at the next reboot.
The operation has completed successfully.
#

/proc/mounts

# cat /proc/mounts
...
/dev/sdb1 /var/lib/ceph/osd/ceph-0 xfs rw,noatime,attr2,inode64,noquota 0 0
#

ls -al

# ls -al /var/lib/ceph/osd/ceph-0
total 56
drwxr-xr-x 2 ceph ceph  234 Nov 24 15:25 .
drwxr-x--- 3 ceph ceph 4096 Nov 24 15:02 ..
-rw-r--r-- 1 root root  366 Nov 24 15:25 activate.monmap
-rw-r--r-- 1 ceph ceph    3 Nov 24 15:25 active
lrwxrwxrwx 1 ceph ceph   58 Nov 24 15:24 block -> /dev/disk/by-partuuid/8743f1a7-0486-4d65-ac6b-e7cc8fe66ba4
-rw-r--r-- 1 ceph ceph   37 Nov 24 15:24 block_uuid
-rw-r--r-- 1 ceph ceph    2 Nov 24 15:25 bluefs
-rw-r--r-- 1 ceph ceph   37 Nov 24 15:24 ceph_fsid
-rw-r--r-- 1 ceph ceph   37 Nov 24 15:24 fsid
-rw------- 1 ceph ceph   56 Nov 24 15:25 keyring
-rw-r--r-- 1 ceph ceph    8 Nov 24 15:25 kv_backend
-rw-r--r-- 1 ceph ceph   21 Nov 24 15:24 magic
-rw-r--r-- 1 ceph ceph    4 Nov 24 15:25 mkfs_done
-rw-r--r-- 1 ceph ceph    6 Nov 24 15:25 ready
-rw-r--r-- 1 ceph ceph    0 Nov 24 15:25 systemd
-rw-r--r-- 1 ceph ceph   10 Nov 24 15:24 type
-rw-r--r-- 1 ceph ceph    2 Nov 24 15:25 whoami
#

What's in the data directory now

# cd /var/lib/ceph/osd/ceph-0/
# cat active
ok
# cat block_uuid
8743f1a7-0486-4d65-ac6b-e7cc8fe66ba4
# cat bluefs
1
# cat ceph_fsid
33e177d8-d6a4-4f75-8e19-535cd50b77a3
# cat /etc/ceph/ceph.conf
fsid = 33e177d8-d6a4-4f75-8e19-535cd50b77a3

auth cluster required = cephx
auth service required = cephx
auth client required = cephx

mon initial members = c1, c2, c3
mon host = 192.168.250.31, 192.168.250.32, 192.168.250.33
# cat fsid
d9809839-e28b-44f6-945f-c69538a41657
# blkid /dev/sdb1
/dev/sdb1: UUID="7bebdf5d-4dbf-440a-a4fc-f1e342edf575" TYPE="xfs" PARTLABEL="ceph data" PARTUUID="d9809839-e28b-44f6-945f-c69538a41657" 
# cat kv_backend
rocksdb
# cat mkfs_done
yes
# cat ready
ready
# cat type
bluestore
# cat whoami
0
# gdisk /dev/sdb
GPT fdisk (gdisk) version 0.8.6

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.

Command (? for help): i
Partition number (1-2): 1
Partition GUID code: 4FBD7E29-9D25-41B8-AFD0-062C0CEFF05D (Unknown)
Partition unique GUID: D9809839-E28B-44F6-945F-C69538A41657
First sector: 2048 (at 1024.0 KiB)
Last sector: 206847 (at 101.0 MiB)
Partition size: 204800 sectors (100.0 MiB)
Attribute flags: 0000000000000000
Partition name: 'ceph data'

Command (? for help): i
Partition number (1-2): 2
Partition GUID code: CAFECAFE-9B03-4F30-B4C6-B4B80CEFF106 (Unknown)
Partition unique GUID: 8743F1A7-0486-4D65-AC6B-E7CC8FE66BA4
First sector: 206848 (at 101.0 MiB)
Last sector: 209715166 (at 100.0 GiB)
Partition size: 209508319 sectors (99.9 GiB)
Attribute flags: 0000000000000000
Partition name: 'ceph block'

Command (? for help): q
[root@c3 ceph-0]#