Re: Filestore OSD on CephFS?

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How can there be a "catastrophic reason" if you have "no active, 
production workload"...? Do as you please. I am also having 1 
replication for temp en tests. But if you have only one osd why use 
ceph? Choose the correct 'tool' for the job.





-----Original Message-----
From: Kenneth Van Alstyne [mailto:kvanalstyne@xxxxxxxxxxxxxxx] 
Sent: 16 January 2019 15:04
To: ceph-users
Subject:  Filestore OSD on CephFS?

Disclaimer:  Even I will admit that I know this is going to sound like a 
silly/crazy/insane question, but I have a reason for wanting to do this 
and asking the question.  Its also worth noting that no active, 
production workload will be used on this cluster, so Im worried 
more about data integrity than performance of availability. 

Can anyone think of any catastrophic reason why I cannot use an existing 
clusters CephFS filesystem as a single OSD for a small cluster?  Ive 
tested it and it seems to work with the following caveats:
- 50% performance degradation (due to double write penalty since journal 
and OSD data both are on the same backing cluster)
- Max object name and namespace length limits, which can be overcome 
with the following OSD parameters:
- osd max object name len = 256
- osd max object namespace len = 64
- Due to above name/namespace length limits, cluster should be limited 
to RBD (which is exactly what I want to do)

Some details of my cluster are below if anyone cares and Im getting a 
consistent, solid roughly 50% of the underlying clusters performance 
benchmarks using rados bench:
# ceph --cluster cephfs status
  cluster:
    id:     0f8904ce-754b-48d4-aa58-7ee6fe9e2cca
    health: HEALTH_OK
 
  services:
    mon:        1 daemons, quorum storage
    mgr:        storage(active)
    osd:        1 osds: 1 up, 1 in
    rbd-mirror: 1 daemon active
 
  data:
    pools:   1 pools, 32 pgs
    objects: 10  objects, 133 B
    usage:   12 MiB used, 87 GiB / 87 GiB avail
    pgs:     32 active+clean
 
  io:
    client:   85 B/s wr, 0 op/s rd, 0 op/s wr
 
# ceph --cluster cephfs versions
{
    "mon": {
        "ceph version 13.2.4 (b10be4d44915a4d78a8e06aa31919e74927b142e) 
mimic (stable)": 1
    },
    "mgr": {
        "ceph version 13.2.4 (b10be4d44915a4d78a8e06aa31919e74927b142e) 
mimic (stable)": 1
    },
    "osd": {
        "ceph version 13.2.4 (b10be4d44915a4d78a8e06aa31919e74927b142e) 
mimic (stable)": 1
    },
    "mds": {},
    "rbd-mirror": {
        "ceph version 13.2.4 (b10be4d44915a4d78a8e06aa31919e74927b142e) 
mimic (stable)": 1
    },
    "overall": {
        "ceph version 13.2.4 (b10be4d44915a4d78a8e06aa31919e74927b142e) 
mimic (stable)": 4
    }
}


# ceph --cluster cephfs osd df
ID CLASS WEIGHT  REWEIGHT SIZE   USE    AVAIL  %USE VAR  PGS 
 0   hdd 0.08510  1.00000 87 GiB 16 MiB 87 GiB 0.02 1.00  32 
                    TOTAL 87 GiB 16 MiB 87 GiB 0.02          
MIN/MAX VAR: 1.00/1.00  STDDEV: 0


# ceph --cluster cephfs df
GLOBAL:
    SIZE       AVAIL      RAW USED     %RAW USED 
    87 GiB     87 GiB       16 MiB          0.02 
POOLS:
    NAME     ID     USED      %USED     MAX AVAIL     OBJECTS 
    rbd      1      133 B         0        83 GiB          10 


# df -h /var/lib/ceph/osd/cephfs-0/
Filesystem             Size  Used Avail Use% Mounted on
10.0.0.1:/ceph-remote   87G   12M   87G   1% /var/lib/ceph

Thanks,

--
Kenneth Van Alstyne
Systems Architect
Knight Point Systems, LLC
Service-Disabled Veteran-Owned Business
1775 Wiehle Avenue Suite 101 | Reston, VA 20190
c: 228-547-8045 f: 571-266-3106
www.knightpoint.com
DHS EAGLE II Prime Contractor: FC1 SDVOSB Track GSA Schedule 70 SDVOSB: 
GS-35F-0646S GSA MOBIS Schedule: GS-10F-0404Y ISO 9001 / ISO 20000 / ISO 
27001 / CMMI Level 3

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