pveceph: followup: refactor advantage list

[pve-docs.git] / pveceph.adoc

[[chapter_pveceph]]
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pveceph(1)
==========
:pve-toplevel:

NAME
----

pveceph - Manage Ceph Services on Proxmox VE Nodes

SYNOPSIS
--------

include::pveceph.1-synopsis.adoc[]

DESCRIPTION
-----------
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Manage Ceph Services on Proxmox VE Nodes
========================================
:pve-toplevel:
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[thumbnail="gui-ceph-status.png"]

{pve} unifies your compute and storage systems, i.e. you can use the same
physical nodes within a cluster for both computing (processing VMs and
containers) and replicated storage. The traditional silos of compute and
storage resources can be wrapped up into a single hyper-converged appliance.
Separate storage networks (SANs) and connections via network attached storages
(NAS) disappear. With the integration of Ceph, an open source software-defined
storage platform, {pve} has the ability to run and manage Ceph storage directly
on the hypervisor nodes.

Ceph is a distributed object store and file system designed to provide
excellent performance, reliability and scalability.

.Some advantages of Ceph on {pve} are:
- Easy setup and management with CLI and GUI support
- Thin provisioning
- Snapshots support
- Self healing
- Scalable to the exabyte level
- Setup pools with different performance and redundancy characteristics
- Data is replicated, making it fault tolerant
- Runs on economical commodity hardware
- No need for hardware RAID controllers
- Open source

For small to mid sized deployments, it is possible to install a Ceph server for
RADOS Block Devices (RBD) directly on your {pve} cluster nodes, see
xref:ceph_rados_block_devices[Ceph RADOS Block Devices (RBD)]. Recent
hardware has plenty of CPU power and RAM, so running storage services
and VMs on the same node is possible.

To simplify management, we provide 'pveceph' - a tool to install and
manage {ceph} services on {pve} nodes.

.Ceph consists of a couple of Daemons footnote:[Ceph intro http://docs.ceph.com/docs/master/start/intro/], for use as a RBD storage:
- Ceph Monitor (ceph-mon)
- Ceph Manager (ceph-mgr)
- Ceph OSD (ceph-osd; Object Storage Daemon)

TIP: We recommend to get familiar with the Ceph vocabulary.
footnote:[Ceph glossary http://docs.ceph.com/docs/luminous/glossary]


Precondition
------------

To build a Proxmox Ceph Cluster there should be at least three (preferably)
identical servers for the setup.

A 10Gb network, exclusively used for Ceph, is recommended. A meshed network
setup is also an option if there are no 10Gb switches available, see our wiki
article footnote:[Full Mesh Network for Ceph {webwiki-url}Full_Mesh_Network_for_Ceph_Server] .

Check also the recommendations from
http://docs.ceph.com/docs/luminous/start/hardware-recommendations/[Ceph's website].

.Avoid RAID
While RAID controller are build for storage virtualisation, to combine
independent disks to form one or more logical units. Their caching methods,
algorithms (RAID modes; incl. JBOD), disk or write/read optimisations are
targeted towards aforementioned logical units and not to Ceph.

WARNING: Avoid RAID controller, use host bus adapter (HBA) instead.


Installation of Ceph Packages
-----------------------------

On each node run the installation script as follows:

[source,bash]
----
pveceph install
----

This sets up an `apt` package repository in
`/etc/apt/sources.list.d/ceph.list` and installs the required software.


Creating initial Ceph configuration
-----------------------------------

[thumbnail="gui-ceph-config.png"]

After installation of packages, you need to create an initial Ceph
configuration on just one node, based on your network (`10.10.10.0/24`
in the following example) dedicated for Ceph:

[source,bash]
----
pveceph init --network 10.10.10.0/24
----

This creates an initial configuration at `/etc/pve/ceph.conf`. That file is
automatically distributed to all {pve} nodes by using
xref:chapter_pmxcfs[pmxcfs]. The command also creates a symbolic link
from `/etc/ceph/ceph.conf` pointing to that file. So you can simply run
Ceph commands without the need to specify a configuration file.


[[pve_ceph_monitors]]
Creating Ceph Monitors
----------------------

[thumbnail="gui-ceph-monitor.png"]

The Ceph Monitor (MON)
footnote:[Ceph Monitor http://docs.ceph.com/docs/luminous/start/intro/]
maintains a master copy of the cluster map. For high availability you need to
have at least 3 monitors.

On each node where you want to place a monitor (three monitors are recommended),
create it by using the 'Ceph -> Monitor' tab in the GUI or run.


[source,bash]
----
pveceph createmon
----

This will also install the needed Ceph Manager ('ceph-mgr') by default. If you
do not want to install a manager, specify the '-exclude-manager' option.


[[pve_ceph_manager]]
Creating Ceph Manager
----------------------

The Manager daemon runs alongside the monitors, providing an interface for
monitoring the cluster. Since the Ceph luminous release the
ceph-mgr footnote:[Ceph Manager http://docs.ceph.com/docs/luminous/mgr/] daemon
is required. During monitor installation the ceph manager will be installed as
well.

NOTE: It is recommended to install the Ceph Manager on the monitor nodes. For
high availability install more then one manager.

[source,bash]
----
pveceph createmgr
----


[[pve_ceph_osds]]
Creating Ceph OSDs
------------------

[thumbnail="gui-ceph-osd-status.png"]

via GUI or via CLI as follows:

[source,bash]
----
pveceph createosd /dev/sd[X]
----

TIP: We recommend a Ceph cluster size, starting with 12 OSDs, distributed evenly
among your, at least three nodes (4 OSDs on each node).

If the disk was used before (eg. ZFS/RAID/OSD), to remove partition table, boot
sector and any OSD leftover the following commands should be sufficient.

[source,bash]
----
dd if=/dev/zero of=/dev/sd[X] bs=1M count=200
ceph-disk zap /dev/sd[X]
----

WARNING: The above commands will destroy data on the disk!

Ceph Bluestore
~~~~~~~~~~~~~~

Starting with the Ceph Kraken release, a new Ceph OSD storage type was
introduced, the so called Bluestore
footnote:[Ceph Bluestore http://ceph.com/community/new-luminous-bluestore/].
This is the default when creating OSDs in Ceph luminous.

[source,bash]
----
pveceph createosd /dev/sd[X]
----

NOTE: In order to select a disk in the GUI, to be more failsafe, the disk needs
to have a GPT footnoteref:[GPT, GPT partition table
https://en.wikipedia.org/wiki/GUID_Partition_Table] partition table. You can
create this with `gdisk /dev/sd(x)`. If there is no GPT, you cannot select the
disk as DB/WAL.

If you want to use a separate DB/WAL device for your OSDs, you can specify it
through the '-journal_dev' option. The WAL is placed with the DB, if not
specified separately.

[source,bash]
----
pveceph createosd /dev/sd[X] -journal_dev /dev/sd[Y]
----

NOTE: The DB stores BlueStore’s internal metadata and the WAL is BlueStore’s
internal journal or write-ahead log. It is recommended to use a fast SSDs or
NVRAM for better performance.


Ceph Filestore
~~~~~~~~~~~~~
Till Ceph luminous, Filestore was used as storage type for Ceph OSDs. It can
still be used and might give better performance in small setups, when backed by
a NVMe SSD or similar.

[source,bash]
----
pveceph createosd /dev/sd[X] -bluestore 0
----

NOTE: In order to select a disk in the GUI, the disk needs to have a
GPT footnoteref:[GPT] partition table. You can
create this with `gdisk /dev/sd(x)`. If there is no GPT, you cannot select the
disk as journal. Currently the journal size is fixed to 5 GB.

If you want to use a dedicated SSD journal disk:

[source,bash]
----
pveceph createosd /dev/sd[X] -journal_dev /dev/sd[Y] -bluestore 0
----

Example: Use /dev/sdf as data disk (4TB) and /dev/sdb is the dedicated SSD
journal disk.

[source,bash]
----
pveceph createosd /dev/sdf -journal_dev /dev/sdb -bluestore 0
----

This partitions the disk (data and journal partition), creates
filesystems and starts the OSD, afterwards it is running and fully
functional.

NOTE: This command refuses to initialize disk when it detects existing data. So
if you want to overwrite a disk you should remove existing data first. You can
do that using: 'ceph-disk zap /dev/sd[X]'

You can create OSDs containing both journal and data partitions or you
can place the journal on a dedicated SSD. Using a SSD journal disk is
highly recommended to achieve good performance.


[[pve_ceph_pools]]
Creating Ceph Pools
-------------------

[thumbnail="gui-ceph-pools.png"]

A pool is a logical group for storing objects. It holds **P**lacement
**G**roups (PG), a collection of objects.

When no options are given, we set a
default of **64 PGs**, a **size of 3 replicas** and a **min_size of 2 replicas**
for serving objects in a degraded state.

NOTE: The default number of PGs works for 2-6 disks. Ceph throws a
"HEALTH_WARNING" if you have too few or too many PGs in your cluster.

It is advised to calculate the PG number depending on your setup, you can find
the formula and the PG calculator footnote:[PG calculator
http://ceph.com/pgcalc/] online. While PGs can be increased later on, they can
never be decreased.


You can create pools through command line or on the GUI on each PVE host under
**Ceph -> Pools**.

[source,bash]
----
pveceph createpool <name>
----

If you would like to automatically get also a storage definition for your pool,
active the checkbox "Add storages" on the GUI or use the command line option
'--add_storages' on pool creation.

Further information on Ceph pool handling can be found in the Ceph pool
operation footnote:[Ceph pool operation
http://docs.ceph.com/docs/luminous/rados/operations/pools/]
manual.

Ceph CRUSH & device classes
---------------------------
The foundation of Ceph is its algorithm, **C**ontrolled **R**eplication
**U**nder **S**calable **H**ashing
(CRUSH footnote:[CRUSH https://ceph.com/wp-content/uploads/2016/08/weil-crush-sc06.pdf]).

CRUSH calculates where to store to and retrieve data from, this has the
advantage that no central index service is needed. CRUSH works with a map of
OSDs, buckets (device locations) and rulesets (data replication) for pools.

NOTE: Further information can be found in the Ceph documentation, under the
section CRUSH map footnote:[CRUSH map http://docs.ceph.com/docs/luminous/rados/operations/crush-map/].

This map can be altered to reflect different replication hierarchies. The object
replicas can be separated (eg. failure domains), while maintaining the desired
distribution.

A common use case is to use different classes of disks for different Ceph pools.
For this reason, Ceph introduced the device classes with luminous, to
accommodate the need for easy ruleset generation.

The device classes can be seen in the 'ceph osd tree' output. These classes
represent their own root bucket, which can be seen with the below command.

[source, bash]
----
ceph osd crush tree --show-shadow
----

Example output form the above command:

[source, bash]
----
ID  CLASS WEIGHT  TYPE NAME
-16  nvme 2.18307 root default~nvme
-13  nvme 0.72769     host sumi1~nvme
 12  nvme 0.72769         osd.12
-14  nvme 0.72769     host sumi2~nvme
 13  nvme 0.72769         osd.13
-15  nvme 0.72769     host sumi3~nvme
 14  nvme 0.72769         osd.14
 -1       7.70544 root default
 -3       2.56848     host sumi1
 12  nvme 0.72769         osd.12
 -5       2.56848     host sumi2
 13  nvme 0.72769         osd.13
 -7       2.56848     host sumi3
 14  nvme 0.72769         osd.14
----

To let a pool distribute its objects only on a specific device class, you need
to create a ruleset with the specific class first.

[source, bash]
----
ceph osd crush rule create-replicated <rule-name> <root> <failure-domain> <class>
----

[frame="none",grid="none", align="left", cols="30%,70%"]
|===
|<rule-name>|name of the rule, to connect with a pool (seen in GUI & CLI)
|<root>|which crush root it should belong to (default ceph root "default")
|<failure-domain>|at which failure-domain the objects should be distributed (usually host)
|<class>|what type of OSD backing store to use (eg. nvme, ssd, hdd)
|===

Once the rule is in the CRUSH map, you can tell a pool to use the ruleset.

[source, bash]
----
ceph osd pool set <pool-name> crush_rule <rule-name>
----

TIP: If the pool already contains objects, all of these have to be moved
accordingly. Depending on your setup this may introduce a big performance hit on
your cluster. As an alternative, you can create a new pool and move disks
separately.


Ceph Client
-----------

[thumbnail="gui-ceph-log.png"]

You can then configure {pve} to use such pools to store VM or
Container images. Simply use the GUI too add a new `RBD` storage (see
section xref:ceph_rados_block_devices[Ceph RADOS Block Devices (RBD)]).

You also need to copy the keyring to a predefined location for a external Ceph
cluster. If Ceph is installed on the Proxmox nodes itself, then this will be
done automatically.

NOTE: The file name needs to be `<storage_id> + `.keyring` - `<storage_id>` is
the expression after 'rbd:' in `/etc/pve/storage.cfg` which is
`my-ceph-storage` in the following example:

[source,bash]
----
mkdir /etc/pve/priv/ceph
cp /etc/ceph/ceph.client.admin.keyring /etc/pve/priv/ceph/my-ceph-storage.keyring
----


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