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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. It’s also worth noting that no active, production workload will be used on this “cluster”,
so I’m worried more about data integrity than performance of availability.
Can anyone think of any catastrophic reason why I cannot use an existing cluster’s CephFS filesystem as a single OSD for a small cluster? I’ve 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 I’m getting a consistent, solid roughly 50% of the underlying cluster’s 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 Notice: This e-mail message, including any attachments, is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, copy, use, disclosure, or distribution is STRICTLY prohibited. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message. |
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