CentOS 8
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Ceph Octopus : Use Block Device
2020/07/06
 
Configure a Client Host [dlp] to use Ceph Storage like follows.
                                         |
        +--------------------+           |
        |   [dlp.srv.world]  |10.0.0.30  |
        |     Ceph Client    +-----------+
        |                    |           |
        +--------------------+           |
            +----------------------------+----------------------------+
            |                            |                            |
            |10.0.0.51                   |10.0.0.52                   |10.0.0.53 
+-----------+-----------+    +-----------+-----------+    +-----------+-----------+
|   [node01.srv.world]  |    |   [node02.srv.world]  |    |   [node03.srv.world]  |
|     Object Storage    +----+     Object Storage    +----+     Object Storage    |
|     Monitor Daemon    |    |                       |    |                       |
|     Manager Daemon    |    |                       |    |                       |
+-----------------------+    +-----------------------+    +-----------------------+

 
For exmaple, Create a block device and mount it on a Client Host.
[1] Transfer SSH public key to Client Host and Configure it from Admin Node.
# transfer public key

[root@node01 ~]#
ssh-copy-id dlp

# install required packages

[root@node01 ~]#
ssh dlp "dnf -y install centos-release-ceph-octopus epel-release"

[root@node01 ~]#
ssh dlp "dnf -y install ceph-common"
# transfer required files to Client Host

[root@node01 ~]#
scp /etc/ceph/ceph.conf dlp:/etc/ceph/

ceph.conf                                     100%  195    98.1KB/s   00:00
[root@node01 ~]#
scp /etc/ceph/ceph.client.admin.keyring dlp:/etc/ceph/

ceph.client.admin.keyring                     100%  151    71.5KB/s   00:00
[root@node01 ~]#
ssh dlp "chown ceph. /etc/ceph/ceph.*"

[2] Create a Block device and mount it on a Client Host.
# create default RBD pool [rbd]

[root@dlp ~]#
ceph osd pool create rbd 128

pool 'rbd' created
# enable Placement Groups auto scale mode

[root@dlp ~]#
ceph osd pool set rbd pg_autoscale_mode on

set pool 2 pg_autoscale_mode to on
# initialize the pool

[root@dlp ~]#
rbd pool init rbd

[root@dlp ~]#
ceph osd pool autoscale-status

POOL                     SIZE  TARGET SIZE  RATE  RAW CAPACITY   RATIO  TARGET RATIO  EFFECTIVE RATIO  BIAS  PG_NUM  NEW PG_NUM  AUTOSCALE
device_health_metrics      0                 3.0        239.9G  0.0000                                  1.0       1              on
rbd                       19                 3.0        239.9G  0.0000                                  1.0      32              on

# create a block device with 10G

[root@dlp ~]#
rbd create --size 10G --pool rbd rbd01
# confirm

[root@dlp ~]#
rbd ls -l

NAME   SIZE    PARENT  FMT  PROT  LOCK
rbd01  10 GiB            2

# map the block device

[root@dlp ~]#
rbd map rbd01

/dev/rbd0
# confirm

[root@dlp ~]#
rbd showmapped

id  pool  namespace  image  snap  device
0   rbd              rbd01  -     /dev/rbd0

# format with XFS

[root@dlp ~]#
mkfs.xfs /dev/rbd0

meta-data=/dev/rbd0              isize=512    agcount=16, agsize=163840 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=0
         =                       reflink=1
data     =                       bsize=4096   blocks=2621440, imaxpct=25
         =                       sunit=16     swidth=16 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=2560, version=2
         =                       sectsz=512   sunit=16 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

[root@dlp ~]#
mount /dev/rbd0 /mnt

[root@dlp ~]#
df -hT

Filesystem          Type      Size  Used Avail Use% Mounted on
devtmpfs            devtmpfs  3.8G     0  3.8G   0% /dev
tmpfs               tmpfs     3.9G     0  3.9G   0% /dev/shm
tmpfs               tmpfs     3.9G  8.5M  3.9G   1% /run
tmpfs               tmpfs     3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/mapper/cl-root xfs        26G  1.9G   25G   8% /
/dev/vda1           ext4      976M  259M  651M  29% /boot
tmpfs               tmpfs     781M     0  781M   0% /run/user/0
/dev/rbd0           xfs        10G  105M  9.9G   2% /mnt
[3] For delete Block devices or Pools you created, run commands like follows.
For deleting Pools, it needs to set [mon allow pool delete = true] on [Monitor Daemon] configuration.
# unmap

[root@dlp ~]#
rbd unmap /dev/rbd/rbd/rbd01
# delete a block device

[root@dlp ~]#
rbd rm rbd01 -p rbd

Removing image: 100% complete...done.
# delete a pool

# ceph osd pool delete [Pool Name] [Pool Name] ***

[root@dlp ~]#
ceph osd pool delete rbd rbd --yes-i-really-really-mean-it

pool 'rbd' removed
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