[ceph-users] Ceph space problem, garbage collector ?

[Olivier Bonvalet]

Hi,

I have a space problem on a production cluster, like if there is unused
data not freed : "ceph df" and "rados df" reports 613GB of data, and
disk usage is 2640GB (with 3 replica). It should be near 1839GB.


I have 5 hosts, 3 with SAS storage and 2 with SSD storage. I use crush
rules to put pools on SAS or on SSD.

My pools :
# ceph osd dump | grep ^pool
pool 0 'data' rep size 3 min_size 1 crush_ruleset 0 object_hash rjenkins pg_num 
576 pgp_num 576 last_change 68315 owner 0 crash_replay_interval 45
pool 1 'metadata' rep size 3 min_size 1 crush_ruleset 1 object_hash rjenkins 
pg_num 576 pgp_num 576 last_change 68317 owner 0
pool 2 'rbd' rep size 3 min_size 1 crush_ruleset 2 object_hash rjenkins pg_num 
576 pgp_num 576 last_change 68321 owner 0
pool 3 'hdd3copies' rep size 3 min_size 1 crush_ruleset 4 object_hash rjenkins 
pg_num 200 pgp_num 200 last_change 172933 owner 0
pool 6 'ssd3copies' rep size 3 min_size 1 crush_ruleset 7 object_hash rjenkins 
pg_num 800 pgp_num 800 last_change 172929 owner 0
pool 9 'sas3copies' rep size 3 min_size 1 crush_ruleset 4 object_hash rjenkins 
pg_num 2048 pgp_num 2048 last_change 172935 owner 0

Only hdd3copies, sas3copies and ssd3copies are really used :
# ceph df
GLOBAL:
    SIZE       AVAIL      RAW USED     %RAW USED 
    76498G     51849G     24648G       32.22     

POOLS:
    NAME           ID     USED      %USED     OBJECTS 
    data           0      46753     0         72      
    metadata       1      0         0         0       
    rbd            2      8         0         1       
    hdd3copies     3      2724G     3.56      5190954 
    ssd3copies     6      613G      0.80      347668  
    sas3copies     9      3692G     4.83      764394  


My CRUSH rules was :

rule SASperHost {
        ruleset 4
        type replicated
        min_size 1
        max_size 10
        step take SASroot
        step chooseleaf firstn 0 type host
        step emit
}

and :

rule SSDperOSD {
        ruleset 3
        type replicated
        min_size 1
        max_size 10
        step take SSDroot
        step choose firstn 0 type osd
        step emit
}


but, since the cluster was full because of that space problem, I swith to a 
different rule :

rule SSDperOSDfirst {
        ruleset 7
        type replicated
        min_size 1
        max_size 10
        step take SSDroot
        step choose firstn 1 type osd
        step emit
        step take SASroot
        step chooseleaf firstn -1 type net
        step emit
}


So with that last rule, I should have only one replica on my SSD OSD, so 613GB 
of space used. But if I check on OSD I see 1212GB really used.

I also use snapshots, maybe snapshots are ignored by "ceph df" and "rados df" ?

Thanks for any help.

Olivier

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