From: Zac Dover Date: Sun, 2 Jun 2024 11:06:25 +0000 (+1000) Subject: doc/start: Add Beginner's Guide X-Git-Tag: v20.0.0~1834^2 X-Git-Url: http://git.apps.os.sepia.ceph.com/?a=commitdiff_plain;h=91aafc6a7f72c105fbf3aa8419863e931d5b9e00;p=ceph.git doc/start: Add Beginner's Guide Add a Beginner's Guide to docs.ceph.com. Signed-off-by: Zac Dover --- diff --git a/doc/start/beginners-guide.rst b/doc/start/beginners-guide.rst new file mode 100644 index 0000000000000..1d29d6d3be023 --- /dev/null +++ b/doc/start/beginners-guide.rst @@ -0,0 +1,92 @@ +========================== + Beginner's Guide +========================== + +The purpose of A Beginner's Guide to Ceph is to make Ceph comprehensible. + +Ceph is a clustered and distributed storage manager. If that's too cryptic, +then just think of Ceph as a computer program that stores data and uses a +network to make sure that there is a backup copy of the data. + +Ceph offers several "storage interfaces", which is another +way of saying "ways of storing data". These storage interfaces include: +- CephFS (a file system) +- RBD (block devices) +- RADOS (an object store). + +Deep down, though, all three of these are really RADOS object stores. CephFS +and RBD are just presenting themselves as file systems and block devices. + +Ceph is a clustered and distributed storage manager that offers data +redundancy. This sentence might be too cryptic for first-time readers of the +Ceph Beginner's Guide, so let's explain all of the terms in it: + +- **Storage Manager.** Ceph is a storage manager. This means that Ceph is + software that helps storage resources store data. Storage resources come in + several forms: hard disk drives (HDD), solid-state drives (SSD), magnetic + tape, floppy disks, punched tape, Hoellerith-style punch cards, and magnetic + drum memory are all forms of storage resources. In this beginner's guide, + we'll focus on hard disk drives (HDD) and solid-state drives (SSD). +- **Clustered storage manager** Ceph is a clustered storage manager. That means + that the storage manager installed not just on a single machine but on + several machines that work together as a system. +- **Distributed storage manager.** Ceph is a clustered and distributed storage + manager. That means that the data that is stored and the infrastructure that + supports it is spread across multiple machines and is not centralized in a + single machine. To better understand what distributed means in this context, + it might be helpful to describe what it is not: it is not a system ISCSI, + which is a system that exposes a single logical disk over the network in a + 1:1 (one-to-one) mapping. +- **Data Redundancy.** Having a second copy of your data somewhere. + +Ceph Monitor +------------ + +The Ceph Monitor is one of the daemons essential to the functioning of a Ceph +cluster. Monitors know the location of all the data in the Ceph cluster. +Monitors maintain maps of the cluster state, and those maps make it possible +for Ceph daemons to work together. These maps include the monitor map, the OSD +map, the MDS map, and the CRUSH map. Three monitors are required to reach +quorum. Quorum is a state that is necessary for a Ceph cluster to work +properly. Quorum means that a majority of the monitors are in the "up" state. + +MANAGER +------- +The manager balances the data in the Ceph cluster, distributing load evenly so +that no part of the cluster gets overloaded. The manager is one of the daemons +essential to the functioning of the Ceph cluster. Managers keep track of +runtime metrics, system utilization, CPU performance, disk load, and they host +the Ceph dashboard web GUI. + +OSD +--- + +Object Storage Daemons (OSDs) store objects. + +An OSD is a process that runs on a storage server. The OSD is responsible for +managing a single unit of storage, which is usually a single disk. + +POOLS +----- + +A pool is an abstraction that can be designated as either "replicated" or +"erasure coded". In Ceph, the method of data protection is set at the pool +level. Ceph offers and supports two types of data protection: replication and +erasure coding. Objects are stored in pools. "A storage pool is a collection of +storage volumes. A storage volume is the basic unit of storage, such as +allocated space on a disk or a single tape cartridge. The server uses the +storage volumes to store backed-up, archived, or space-managed files." (IBM +Tivoli Storage Manager, Version 7.1, "Storage Pools") + +PLACEMENT GROUPS +---------------- + +Placement groups are a part of pools. + +MDS +--- +A metadata server (MDS) is necessary for the proper functioning of CephFS. +See :ref:`orchestrator-cli-cephfs` and :ref:`arch-cephfs`. + + + diff --git a/doc/start/intro.rst b/doc/start/intro.rst index 390f1b2d8d52d..1cbead4a3df0b 100644 --- a/doc/start/intro.rst +++ b/doc/start/intro.rst @@ -78,6 +78,7 @@ recover dynamically. .. toctree:: :maxdepth: 2 + Beginner's Guide Hardware Recommendations OS Recommendations