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ceph/doc/rados/configuration/network-config-ref.rst
John Wilkins 6640837da3 doc/rados: Removed contractions to improve readabilty for ESL speakers. 
Signed-off-by: John Wilkins <jowilkin@redhat.com>
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=================================
Network Configuration Reference
=================================
Network configuration is critical for building a high performance :term:`Ceph
Storage Cluster`. The Ceph Storage Cluster does not perform request routing or
dispatching on behalf of the :term:`Ceph Client`. Instead, Ceph Clients make
requests directly to Ceph OSD Daemons. Ceph OSD Daemons perform data replication
on behalf of Ceph Clients, which means replication and other factors impose
additional loads on Ceph Storage Cluster networks.
Our Quick Start configurations provide a trivial `Ceph configuration file`_ that
sets monitor IP addresses and daemon host names only. Unless you specify a
cluster network, Ceph assumes a single "public" network. Ceph functions just
fine with a public network only, but you may see significant performance
improvement with a second "cluster" network in a large cluster.
We recommend running a Ceph Storage Cluster with two networks: a public
(front-side) network and a cluster (back-side) network. To support two networks,
each :term:`Ceph Node` will need to have more than one NIC. See `Hardware
Recommendations - Networks`_ for additional details.
.. ditaa::
+-------------+
| Ceph Client |
+----*--*-----+
| ^
Request | : Response
v |
/----------------------------------*--*-------------------------------------\
| Public Network |
\---*--*------------*--*-------------*--*------------*--*------------*--*---/
^ ^ ^ ^ ^ ^ ^ ^ ^ ^
| | | | | | | | | |
| : | : | : | : | :
v v v v v v v v v v
+---*--*---+ +---*--*---+ +---*--*---+ +---*--*---+ +---*--*---+
| Ceph MON | | Ceph MDS | | Ceph OSD | | Ceph OSD | | Ceph OSD |
+----------+ +----------+ +---*--*---+ +---*--*---+ +---*--*---+
^ ^ ^ ^ ^ ^
The cluster network relieves | | | | | |
OSD replication and heartbeat | : | : | :
traffic from the public network. v v v v v v
/------------------------------------*--*------------*--*------------*--*---\
| cCCC Cluster Network |
\---------------------------------------------------------------------------/
There are several reasons to consider operating two separate networks:
#. **Performance:** Ceph OSD Daemons handle data replication for the Ceph
Clients. When Ceph OSD Daemons replicate data more than once, the network
load between Ceph OSD Daemons easily dwarfs the network load between Ceph
Clients and the Ceph Storage Cluster. This can introduce latency and
create a performance problem. Recovery and rebalancing can
also introduce significant latency on the public network. See
`Scalability and High Availability`_ for additional details on how Ceph
replicates data. See `Monitor / OSD Interaction`_ for details on heartbeat
traffic.
#. **Security**: While most people are generally civil, a very tiny segment of
the population likes to engage in what's known as a Denial of Service (DoS)
attack. When traffic between Ceph OSD Daemons gets disrupted, placement
groups may no longer reflect an ``active + clean`` state, which may prevent
users from reading and writing data. A great way to defeat this type of
attack is to maintain a completely separate cluster network that doesn't
connect directly to the internet. Also, consider using `Message Signatures`_
to defeat spoofing attacks.
IP Tables
=========
By default, daemons `bind`_ to ports within the ``6800:7300`` range. You may
configure this range at your discretion. Before configuring your IP tables,
check the default ``iptables`` configuration.
sudo iptables -L
Some Linux distributions include rules that reject all inbound requests
except SSH from all network interfaces. For example::
REJECT all -- anywhere anywhere reject-with icmp-host-prohibited
You will need to delete these rules on both your public and cluster networks
initially, and replace them with appropriate rules when you are ready to
harden the ports on your Ceph Nodes.
Monitor IP Tables
-----------------
Ceph Monitors listen on port ``6789`` by default. Additionally, Ceph Monitors
always operate on the public network. When you add the rule using the example
below, make sure you replace ``{iface}`` with the public network interface
(e.g., ``eth0``, ``eth1``, etc.), ``{ip-address}`` with the IP address of the
public network and ``{netmask}`` with the netmask for the public network. ::
sudo iptables -A INPUT -i {iface} -p tcp -s {ip-address}/{netmask} --dport 6789 -j ACCEPT
MDS IP Tables
-------------
A :term:`Ceph Metadata Server` listens on the first available port on the public
network beginning at port 6800. Note that this behavior is not deterministic, so
if you are running more than one OSD or MDS on the same host, or if you restart
the daemons within a short window of time, the daemons will bind to higher
ports. You should open the entire 6800-7300 range by default. When you add the
rule using the example below, make sure you replace ``{iface}`` with the public
network interface (e.g., ``eth0``, ``eth1``, etc.), ``{ip-address}`` with the IP
address of the public network and ``{netmask}`` with the netmask of the public
network.
For example::
sudo iptables -A INPUT -i {iface} -m multiport -p tcp -s {ip-address}/{netmask} --dports 6800:7300 -j ACCEPT
OSD IP Tables
-------------
By default, Ceph OSD Daemons `bind`_ to the first available ports on a Ceph Node
beginning at port 6800. Note that this behavior is not deterministic, so if you
are running more than one OSD or MDS on the same host, or if you restart the
daemons within a short window of time, the daemons will bind to higher ports.
Each Ceph OSD Daemon on a Ceph Node may use up to four ports:
#. One for talking to clients and monitors.
#. One for sending data to other OSDs.
#. Two for heartbeating on each interface.
.. ditaa::
/---------------\
| OSD |
| +---+----------------+-----------+
| | Clients & Monitors | Heartbeat |
| +---+----------------+-----------+
| |
| +---+----------------+-----------+
| | Data Replication | Heartbeat |
| +---+----------------+-----------+
| cCCC |
\---------------/
When a daemon fails and restarts without letting go of the port, the restarted
daemon will bind to a new port. You should open the entire 6800-7300 port range
to handle this possibility.
If you set up separate public and cluster networks, you must add rules for both
the public network and the cluster network, because clients will connect using
the public network and other Ceph OSD Daemons will connect using the cluster
network. When you add the rule using the example below, make sure you replace
``{iface}`` with the network interface (e.g., ``eth0``, ``eth1``, etc.),
``{ip-address}`` with the IP address and ``{netmask}`` with the netmask of the
public or cluster network. For example::
sudo iptables -A INPUT -i {iface} -m multiport -p tcp -s {ip-address}/{netmask} --dports 6800:7300 -j ACCEPT
.. tip:: If you run Ceph Metadata Servers on the same Ceph Node as the
Ceph OSD Daemons, you can consolidate the public network configuration step.
Ceph Networks
=============
To configure Ceph networks, you must add a network configuration to the
``[global]`` section of the configuration file. Our 5-minute Quick Start
provides a trivial `Ceph configuration file`_ that assumes one public network
with client and server on the same network and subnet. Ceph functions just fine
with a public network only. However, Ceph allows you to establish much more
specific criteria, including multiple IP network and subnet masks for your
public network. You can also establish a separate cluster network to handle OSD
heartbeat, object replication and recovery traffic. Don't confuse the IP
addresses you set in your configuration with the public-facing IP addresses
network clients may use to access your service. Typical internal IP networks are
often ``192.168.0.0`` or ``10.0.0.0``.
.. tip:: If you specify more than one IP address and subnet mask for
either the public or the cluster network, the subnets within the network
must be capable of routing to each other. Additionally, make sure you
include each IP address/subnet in your IP tables and open ports for them
as necessary.
.. note:: Ceph uses `CIDR`_ notation for subnets (e.g., ``10.0.0.0/24``).
When you have configured your networks, you may restart your cluster or restart
each daemon. Ceph daemons bind dynamically, so you do not have to restart the
entire cluster at once if you change your network configuration.
Public Network
--------------
To configure a public network, add the following option to the ``[global]``
section of your Ceph configuration file.
.. code-block:: ini
[global]
...
public network = {public-network/netmask}
Cluster Network
---------------
If you declare a cluster network, OSDs will route heartbeat, object replication
and recovery traffic over the cluster network. This may improve performance
compared to using a single network. To configure a cluster network, add the
following option to the ``[global]`` section of your Ceph configuration file.
.. code-block:: ini
[global]
...
cluster network = {cluster-network/netmask}
We prefer that the cluster network is **NOT** reachable from the public network
or the Internet for added security.
Ceph Daemons
============
Ceph has one network configuration requirement that applies to all daemons: the
Ceph configuration file **MUST** specify the ``host`` for each daemon. Ceph also
requires that a Ceph configuration file specify the monitor IP address and its
port.
.. important:: Some deployment tools (e.g., ``ceph-deploy``, Chef) may create a
configuration file for you. **DO NOT** set these values if the deployment
tool does it for you.
.. tip:: The ``host`` setting is the short name of the host (i.e., not
an fqdn). It is **NOT** an IP address either. Enter ``hostname -s`` on
the command line to retrieve the name of the host.
.. code-block:: ini
[mon.a]
host = {hostname}
mon addr = {ip-address}:6789
[osd.0]
host = {hostname}
You do not have to set the host IP address for a daemon. If you have a static IP
configuration and both public and cluster networks running, the Ceph
configuration file may specify the IP address of the host for each daemon. To
set a static IP address for a daemon, the following option(s) should appear in
the daemon instance sections of your ``ceph.conf`` file.
.. code-block:: ini
[osd.0]
public addr = {host-public-ip-address}
cluster addr = {host-cluster-ip-address}
.. topic:: One NIC OSD in a Two Network Cluster
Generally, we do not recommend deploying an OSD host with a single NIC in a
cluster with two networks. However, you may accomplish this by forcing the
OSD host to operate on the public network by adding a ``public addr`` entry
to the ``[osd.n]`` section of the Ceph configuration file, where ``n``
refers to the number of the OSD with one NIC. Additionally, the public
network and cluster network must be able to route traffic to each other,
which we don't recommend for security reasons.
Network Config Settings
=======================
Network configuration settings are not required. Ceph assumes a public network
with all hosts operating on it unless you specifically configure a cluster
network.
Public Network
--------------
The public network configuration allows you specifically define IP addresses
and subnets for the public network. You may specifically assign static IP
addresses or override ``public network`` settings using the ``public addr``
setting for a specific daemon.
``public network``
:Description: The IP address and netmask of the public (front-side) network
(e.g., ``192.168.0.0/24``). Set in ``[global]``. You may specify
comma-delimited subnets.
:Type: ``{ip-address}/{netmask} [, {ip-address}/{netmask}]``
:Required: No
:Default: N/A
``public addr``
:Description: The IP address for the public (front-side) network.
Set for each daemon.
:Type: IP Address
:Required: No
:Default: N/A
Cluster Network
---------------
The cluster network configuration allows you to declare a cluster network, and
specifically define IP addresses and subnets for the cluster network. You may
specifically assign static IP addresses or override ``cluster network``
settings using the ``cluster addr`` setting for specific OSD daemons.
``cluster network``
:Description: The IP address and netmask of the cluster (back-side) network
(e.g., ``10.0.0.0/24``). Set in ``[global]``. You may specify
comma-delimited subnets.
:Type: ``{ip-address}/{netmask} [, {ip-address}/{netmask}]``
:Required: No
:Default: N/A
``cluster addr``
:Description: The IP address for the cluster (back-side) network.
Set for each daemon.
:Type: Address
:Required: No
:Default: N/A
Bind
----
Bind settings set the default port ranges Ceph OSD and MDS daemons use. The
default range is ``6800:7300``. Ensure that your `IP Tables`_ configuration
allows you to use the configured port range.
You may also enable Ceph daemons to bind to IPv6 addresses instead of IPv4
addresses.
``ms bind port min``
:Description: The minimum port number to which an OSD or MDS daemon will bind.
:Type: 32-bit Integer
:Default: ``6800``
:Required: No
``ms bind port max``
:Description: The maximum port number to which an OSD or MDS daemon will bind.
:Type: 32-bit Integer
:Default: ``7300``
:Required: No.
``ms bind ipv6``
:Description: Enables Ceph daemons to bind to IPv6 addresses. Currently the
messenger *either* uses IPv4 or IPv6, but it cannot do both.
:Type: Boolean
:Default: ``false``
:Required: No
``public bind addr``
:Description: In some dynamic deployments the Ceph MON daemon might bind
to an IP address locally that is different from the ``public addr``
advertised to other peers in the network. The environment must ensure
that routing rules are set correclty. If ``public bind addr`` is set
the Ceph MON daemon will bind to it locally and use ``public addr``
in the monmaps to advertise its address to peers. This behavior is limited
to the MON daemon.
:Type: IP Address
:Required: No
:Default: N/A
Hosts
-----
Ceph expects at least one monitor declared in the Ceph configuration file, with
a ``mon addr`` setting under each declared monitor. Ceph expects a ``host``
setting under each declared monitor, metadata server and OSD in the Ceph
configuration file. Optionally, a monitor can be assigned with a priority, and
the clients will always connect to the monitor with lower value of priority if
specified.
``mon addr``
:Description: A list of ``{hostname}:{port}`` entries that clients can use to
connect to a Ceph monitor. If not set, Ceph searches ``[mon.*]``
sections.
:Type: String
:Required: No
:Default: N/A
``mon priority``
:Description: The priority of the declared monitor, the lower value the more
prefered when a client selects a monitor when trying to connect
to the cluster.
:Type: Unsigned 16-bit Integer
:Required: No
:Default: 0
``host``
:Description: The hostname. Use this setting for specific daemon instances
(e.g., ``[osd.0]``).
:Type: String
:Required: Yes, for daemon instances.
:Default: ``localhost``
.. tip:: Do not use ``localhost``. To get your host name, execute
``hostname -s`` on your command line and use the name of your host
(to the first period, not the fully-qualified domain name).
.. important:: You should not specify any value for ``host`` when using a third
party deployment system that retrieves the host name for you.
TCP
---
Ceph disables TCP buffering by default.
``ms tcp nodelay``
:Description: Ceph enables ``ms tcp nodelay`` so that each request is sent
immediately (no buffering). Disabling `Nagle's algorithm`_
increases network traffic, which can introduce latency. If you
experience large numbers of small packets, you may try
disabling ``ms tcp nodelay``.
:Type: Boolean
:Required: No
:Default: ``true``
``ms tcp rcvbuf``
:Description: The size of the socket buffer on the receiving end of a network
connection. Disable by default.
:Type: 32-bit Integer
:Required: No
:Default: ``0``
``ms tcp read timeout``
:Description: If a client or daemon makes a request to another Ceph daemon and
does not drop an unused connection, the ``ms tcp read timeout``
defines the connection as idle after the specified number
of seconds.
:Type: Unsigned 64-bit Integer
:Required: No
:Default: ``900`` 15 minutes.
.. _Scalability and High Availability: ../../../architecture#scalability-and-high-availability
.. _Hardware Recommendations - Networks: ../../../start/hardware-recommendations#networks
.. _Ceph configuration file: ../../../start/quick-ceph-deploy/#create-a-cluster
.. _hardware recommendations: ../../../start/hardware-recommendations
.. _Monitor / OSD Interaction: ../mon-osd-interaction
.. _Message Signatures: ../auth-config-ref#signatures
.. _CIDR: http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing
.. _Nagle's Algorithm: http://en.wikipedia.org/wiki/Nagle's_algorithm
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