doc/start: update hardware recs #47109
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This PR picks up the parts of ceph#44466 that were not merged back in January, when that pull request was raised. Matters added here: * improved organzation of matter * emphasis of IOPs per core over cores per OSD Signed-off-by: Zac Dover <zac.dover@gmail.com>
| separate hosts to avoid resource contention. | ||
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| CephFS metadata servers (MDS) are CPU-intensive. CephFS metadata servers (MDS) | ||
| should therefore have quad-core (or better) CPUs and high clock rates (GHz). OSD |
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I think we might do well to be more clear that MDS nodes benefit a lot more from clock rate than from CPUs, so a 4-core 3.5 GHz model would be preferable to an 8-core 2.5 GHz SKU. I think the current MDS may be single-threaded, so maybe something like "(MDS) don't need more than 4 cores, but should have as high a clock rate (GHz) as possible". Or "frequency" instead of "clock rate", I think in terms of the latter, but the former might be more common with our audience.
| should therefore have quad-core (or better) CPUs and high clock rates (GHz). OSD | ||
| nodes need enough processing power to run the RADOS service, to calculate data | ||
| placement with CRUSH, to replicate data, and to maintain their own copies of the | ||
| cluster map. |
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Do we want to mention EC parity / hash computation?
| the number of cores per OSD, but this cores-per-OSD metric is no longer as | ||
| useful a metric as the number of cycles per IOP and the number of IOPs per OSD. | ||
| For example, for NVMe drives, Ceph can easily utilize five or six cores on real | ||
| clusters and up to about fourteen cores on single OSDs in isolation. So cores |
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From discussion with the good Mr. Nelson I know what isolation means here, but I might ask if that info is useful to our readers, or if it might confuse them. I also am often uncertain re whether we're talking about physical cores or [hyper] threads; I suspect these numbers are the latter.
| modest processors. If your host machines will run CPU-intensive processes in | ||
| addition to Ceph daemons, make sure that you have enough processing power to | ||
| run both the CPU-intensive processes and the Ceph daemons. (OpenStack Nova is | ||
| one such example of a CPU-intensive process.) We recommend that you run |
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Maybe drop the parens, since that's a standalone sentence? Or am I being sententious? Maybe word this as "OpenStack nova-compute or Proxmox" -- we seem to see a growing population of Ceph users by virtue of converged Proxmox deployments.
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I think this should be changed to qemu-kvm as an example, and not openstack nova. Nova itself isn't very CPU intensive, but qemu-kvm would cover almost all use cases where ceph would be co-located with virtual machines, including kubernetes situations were vms and osds are residing on the same host.
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See Zac's comment below about a followup issue
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https://tracker.ceph.com/issues/55938 - Anthony's comments are collected in this tracker bug, which is the June 2022 hardware recommendations documentation tracker (and the page on which I track all mid-2022 hardware recommendations documentation updates) |
This PR picks up the parts of
#44466
that were not merged back in January, when that
pull request was raised.
Matters added here:
Signed-off-by: Zac Dover zac.dover@gmail.com
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