CephFS with a Dedicated Pool

This blog is about configuring a dedicated pool ( user defined pool ) for cephfs. If you are looking to configure cephfs , please visit CephFS Step by Step blog

• Create a new pool for cephfs ( obviosly you can use your existing pool )

# rados mkpool cephfs

• Grab pool id

# ceph osd dump | grep -i cephfs
pool 34 'cephfs' rep size 2 min_size 1 crush_ruleset 0 object_hash rjenkins pg_num 8 pgp_num 8 last_change 860 owner 0
#

• Assign the pool to MDS

# ceph mds add_data_pool 34

• Mount your cephfs share

# mount -t ceph 192.168.100.101:/ /cephfs -o name=cephfs,secretfile=/etc/ceph/client.cephfs

• Check current layout of cephfs , you would notice the default layout.data_pool is set to 0 , which means your cephfs will store date in pool 0 i.e data pool

# cephfs /cephfs/ show_layout
layout.data_pool: 0
layout.object_size: 4194304
layout.stripe_unit: 4194304
layout.stripe_count: 1

• Set a new layout for data_pool in cephfs , use pool id of the pool that we have created above.

# cephfs /cephfs/ set_layout -p 34
# cephfs /cephfs/ show_layout
layout.data_pool: 34
layout.object_size: 4194304
layout.stripe_unit: 4194304
layout.stripe_count: 1
[root@na_csc_fedora19 ~]#

• Remount your cephfs share

# umount /cephfs
# mount -t ceph 192.168.100.101:/ /cephfs -o name=cephfs,secretfile=/etc/ceph/client.cephfs

• Check objects that are present in cephfs pool , there should be no object as this is a fresh pool and does not contain any data . But if you look for objects for any other pool , it should contain objects.

# rados --pool=cephfs ls

# rados --pool=metadata ls
1.00000000.inode
100.00000000
100.00000000.inode
1.00000000
2.00000000
200.00000000
this is a tesf fine
200.00000001
600.00000000
601.00000000
602.00000000
603.00000000
604.00000000
605.00000000
606.00000000
607.00000000
608.00000000
609.00000000
mds0_inotable
mds0_sessionmap
mds_anchortable
mds_snaptable

• Go to your cephfs directory and create some files ( put data in your file ) .

# cd /cephfs/
# vi test

• Recheck for objects in cephfs pool , now it will show you objects .

# rados --pool=cephfs ls
10000000005.00000000

Summary is , we have created a new pool named "cephfs" , changed layout of cephfs to store its data in new pool "cephfs" , and finally we saw cephfs data is getting stored in pool named cephfs  ( i know its too more cephfs , read it again if you are sleeping and didn't understand cephfs)