From: Zac Dover Date: Thu, 14 Jul 2022 19:29:11 +0000 (+1000) Subject: doc/start: update hardware recs X-Git-Tag: v17.2.6~130^2~15^2 X-Git-Url: http://git.apps.os.sepia.ceph.com/?a=commitdiff_plain;h=96abca41e70dd637953f876beb4e5054206e6283;p=ceph.git doc/start: update hardware recs This PR picks up the parts of https://github.com/ceph/ceph/pull/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 (cherry picked from commit 29c44a3bd6919f7fc23083d75d22e84c8b51e1c1) --- diff --git a/doc/start/hardware-recommendations.rst b/doc/start/hardware-recommendations.rst index ba92155a5f519..d922c03dc9d5d 100644 --- a/doc/start/hardware-recommendations.rst +++ b/doc/start/hardware-recommendations.rst @@ -21,21 +21,30 @@ data cluster (e.g., OpenStack, CloudStack, etc). CPU === -CephFS metadata servers are CPU intensive, so they should have significant -processing power (e.g., quad core or better CPUs) and benefit from higher clock -rate (frequency in GHz). Ceph OSDs run the :term:`RADOS` service, calculate -data placement with :term:`CRUSH`, replicate data, and maintain their own copy of the -cluster map. Therefore, OSD nodes should have a reasonable amount of processing -power. Requirements vary by use-case; a starting point might be one core per -OSD for light / archival usage, and two cores per OSD for heavy workloads such -as RBD volumes attached to VMs. Monitor / manager nodes do not have heavy CPU -demands so a modest processor can be chosen for them. Also consider whether the -host machine will run CPU-intensive processes in addition to Ceph daemons. For -example, if your hosts will run computing VMs (e.g., OpenStack Nova), you will -need to ensure that these other processes leave sufficient processing power for -Ceph daemons. We recommend running additional CPU-intensive processes on -separate hosts to avoid resource contention. - +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 +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. + +The requirements of one Ceph cluster are not the same as the requirements of +another, but here are some general guidelines. + +In earlier versions of Ceph, we would make hardware recommendations based on +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 +per OSD are no longer as pressing a concern as they were. When selecting +hardware, select for IOPs per core. + +Monitor nodes and manager nodes have no heavy CPU demands and require only +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 +non-Ceph CPU-intensive processes on separate hosts (that is, on hosts that are +not your monitor and manager nodes) in order to avoid resource contention. RAM ===