It's a little tricky. In the upstream lab we don't strictly see an IOPS
or average latency advantage with heavy parallelism by running muliple
OSDs per NVMe drive until per-OSD core counts get very high. There does
seem to be a fairly consistent tail latency advantage even at moderately
low core counts however. Results are here:
https://ceph.io/en/news/blog/2023/reef-osds-per-nvme/
Specifically for jitter, there is probably an advantage to using 2 cores
per OSD unless you are very CPU starved, but how much that actually
helps in practice for a typical production workload is questionable
imho. You do pay some overhead for running 2 OSDs per NVMe as well.
Mark
On 1/17/24 12:24, Anthony D'Atri wrote:
Conventional wisdom is that with recent Ceph releases there is no longer a
clear advantage to this.
On Jan 17, 2024, at 11:56, Peter Sabaini <pe...@sabaini.at> wrote:
One thing that I've heard people do but haven't done personally with fast NVMes
(not familiar with the IronWolf so not sure if they qualify) is partition them
up so that they run more than one OSD (say 2 to 4) on a single NVMe to better
utilize the NVMe bandwidth. See
https://ceph.com/community/bluestore-default-vs-tuned-performance-comparison/
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Head of Research and Development
Clyso GmbH
p: +49 89 21552391 12 | a: Minnesota, USA
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