:pmg-toplevel:
endif::manvolnum[]
-We are living in a world where email becomes more and more important -
-failures in email systems are just not acceptable. To meet these
-requirements we developed the Proxmox HA (High Availability) Cluster.
+We are living in a world where email is becoming more and more important -
+failures in email systems are not acceptable. To meet these
+requirements, we developed the Proxmox HA (High Availability) Cluster.
-The {pmg} HA Cluster consists of a master and several slave nodes
-(minimum one node). Configuration is done on the master. Configuration
-and data is synchronized to all cluster nodes over a VPN tunnel. This
+The {pmg} HA Cluster consists of a master node and several slave nodes
+(minimum one slave node). Configuration is done on the master,
+and data is synchronized to all cluster nodes via a VPN tunnel. This
provides the following advantages:
* centralized configuration management
* high performance
We use a unique application level clustering scheme, which provides
-extremely good performance. Special considerations where taken to make
-management as easy as possible. Complete Cluster setup is done within
-minutes, and nodes automatically reintegrate after temporary failures
+extremely good performance. Special considerations were taken to make
+management as easy as possible. A complete cluster setup is done within
+minutes, and nodes automatically reintegrate after temporary failures,
without any operator interaction.
-image::images/pmg-ha-cluster.png[]
+image::images/Proxmox_HA_cluster_final_1024.png[]
-Hardware requirements
+Hardware Requirements
---------------------
There are no special hardware requirements, although it is highly
-recommended to use fast and reliable server with redundant disks on
+recommended to use fast and reliable server hardware, with redundant disks on
all cluster nodes (Hardware RAID with BBU and write cache enabled).
The HA Cluster can also run in virtualized environments.
Subscriptions
-------------
-Each host in a cluster has its own subscription. If you want support
+Each node in a cluster has its own subscription. If you want support
for a cluster, each cluster node needs to have a valid
subscription. All nodes must have the same subscription level.
-Load balancing
+Load Balancing
--------------
-You can use one of the mechanism described in chapter 9 if you want to
-distribute mail traffic among the cluster nodes. Please note that this
-is not always required, because it is also reasonable to use only one
-node to handle SMTP traffic. The second node is used as quarantine
-host (provide the web interface to user quarantine).
+It is usually advisable to distribute mail traffic among all cluster
+nodes. Please note that this is not always required, because it is
+also reasonable to use only one node to handle SMTP traffic. The
+second node can then be used as a quarantine host, that only provides the web
+interface to the user quarantine.
+The normal mail delivery process looks up DNS Mail Exchange (`MX`)
+records to determine the destination host. An `MX` record tells the
+sending system where to deliver mail for a certain domain. It is also
+possible to have several `MX` records for a single domain, each of which can
+have different priorities. For example, our `MX` record looks like this:
-Cluster administration
+----
+# dig -t mx proxmox.com
+
+;; ANSWER SECTION:
+proxmox.com. 22879 IN MX 10 mail.proxmox.com.
+
+;; ADDITIONAL SECTION:
+mail.proxmox.com. 22879 IN A 213.129.239.114
+----
+
+Notice that there is a single `MX` record for the domain
+`proxmox.com`, pointing to `mail.proxmox.com`. The `dig` command
+automatically outputs the corresponding address record, if it
+exists. In our case it points to `213.129.239.114`. The priority of
+our `MX` record is set to 10 (preferred default value).
+
+
+Hot standby with backup `MX` records
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Many people do not want to install two redundant mail proxies. Instead
+they use the mail proxy of their ISP as a fallback. This can be done
+by adding an additional `MX` record with a lower priority (higher
+number). Continuing from the example above, this would look like:
+
+----
+proxmox.com. 22879 IN MX 100 mail.provider.tld.
+----
+
+In such a setup, your provider must accept mails for your domain and
+forward them to you. Please note that this is not advisable, because
+spam detection needs to be done by the backup `MX` server as well, and
+external servers provided by ISPs usually don't do this.
+
+However, you will never lose mails with such a setup, because the sending Mail
+Transport Agent (MTA) will simply deliver the mail to the backup
+server (mail.provider.tld), if the primary server (mail.proxmox.com) is
+not available.
+
+NOTE: Any reasonable mail server retries mail delivery if the target
+server is not available. {pmg} stores mail and retries delivery
+for up to one week. Thus, you will not lose emails if your mail server is
+down, even if you run a single server setup.
+
+
+Load balancing with `MX` records
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Using your ISP's mail server is not always a good idea, because many
+ISPs do not use advanced spam prevention techniques, or do not filter
+spam at all. It is often better to run a second server yourself to
+avoid lower spam detection rates.
+
+It’s quite simple to set up a high-performance, load-balanced
+mail cluster using `MX` records. You just need to define two `MX`
+records with the same priority. The rest of this section will provide
+a complete example.
+
+First, you need to have at least two working {pmg} servers
+(mail1.example.com and mail2.example.com), configured as a cluster (see
+section xref:pmg_cluster_administration[Cluster Administration]
+below), with each having its own IP address. Let us assume the
+following DNS address records:
+
+----
+mail1.example.com. 22879 IN A 1.2.3.4
+mail2.example.com. 22879 IN A 1.2.3.5
+----
+
+It is always a good idea to add reverse lookup entries (PTR
+records) for those hosts, as many email systems nowadays reject mails
+from hosts without valid PTR records. Then you need to define your `MX`
+records:
+
+----
+example.com. 22879 IN MX 10 mail1.example.com.
+example.com. 22879 IN MX 10 mail2.example.com.
+----
+
+This is all you need. Following this, you will receive mail on both
+hosts, load-balanced using round-robin scheduling. If one host fails,
+the other one is used.
+
+
+Other ways
+~~~~~~~~~~
+
+Multiple address records
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Using several DNS `MX` records can be tedious, if you have many
+domains. It is also possible to use one `MX` record per domain, but
+multiple address records:
+
+----
+example.com. 22879 IN MX 10 mail.example.com.
+mail.example.com. 22879 IN A 1.2.3.4
+mail.example.com. 22879 IN A 1.2.3.5
+----
+
+
+Using firewall features
+^^^^^^^^^^^^^^^^^^^^^^^
+
+Many firewalls can do some kind of RR-Scheduling (round-robin) when
+using DNAT. See your firewall manual for more details.
+
+
+[[pmg_cluster_administration]]
+Cluster Administration
----------------------
-Cluster administration is done with a single command line utility
-called `pmgcm'. So you need to login via ssh to manage the cluster
-setup.
+Cluster administration can be done from the GUI or by using the command-line
+utility `pmgcm`. The CLI tool is a bit more verbose, so we suggest
+to use that if you run into any problems.
-NOTE: Always setup the IP configuration before adding a node to the
+NOTE: Always set up the IP configuration, before adding a node to the
cluster. IP address, network mask, gateway address and hostname can’t
be changed later.
-
Creating a Cluster
~~~~~~~~~~~~~~~~~~
-You can create a cluster from any existing Proxmox host. All data is
+[thumbnail="screenshot/pmg-gui-cluster-panel.png", big=1]
+
+You can create a cluster from any existing {pmg} host. All data is
preserved.
* make sure you have the right IP configuration
- (IP/MASK/GATEWAY/HOSTNAME), because you cannot changed that later
+ (IP/MASK/GATEWAY/HOSTNAME), because you cannot change that later
-* run the cluster creation command:
+* press the create button on the GUI, or run the cluster creation command:
+
----
pmgcm create
----
+NOTE: The node where you run the cluster create command will be the
+'master' node.
+
-List Cluster Status
+Show Cluster Status
~~~~~~~~~~~~~~~~~~~
+The GUI shows the status of all cluster nodes. You can also view this
+using the command-line tool:
+
----
pmgcm status
--NAME(CID)--------------IPADDRESS----ROLE-STATE---------UPTIME---LOAD----MEM---DISK
----
+[[pmgcm_join]]
Adding Cluster Nodes
~~~~~~~~~~~~~~~~~~~~
-When you add a new node to a cluster (join) all data on that node is
-destroyed. The whole database is initialized with cluster data from
+[thumbnail="screenshot/pmg-gui-cluster-join.png", big=1]
+
+When you add a new node to a cluster (using `join`), all data on that node is
+destroyed. The whole database is initialized with the cluster data from
the master.
* make sure you have the right IP configuration
pmgcm join <master_ip>
----
-You need to enter the root password of the master host when asked for
-a password.
+You need to enter the root password of the master host, when asked for
+a password. When joining a cluster using the GUI, you also need to
+enter the 'fingerprint' of the master node. You can get this information
+by pressing the `Add` button on the master node.
+
+NOTE: Joining a cluster with two-factor authentication enabled for the `root`
+user is not supported. Remove the second factor when joining the cluster.
-CAUTION: Node initialization deletes all existing databases, stops and
-then restarts all services accessing the database. So do not add nodes
-which are already active and receive mails.
+CAUTION: Node initialization deletes all existing databases, stops all
+services accessing the database and then restarts them. Therefore, do
+not add nodes which are already active and receive mail.
-Also, joining a cluster can take several minutes, because the new node
-needs to synchronize all data from the master (although this is done
-in the background).
+Also note that joining a cluster can take several minutes, because the
+new node needs to synchronize all data from the master (although this
+is done in the background).
-NOTE: If you join a new node, existing quarantined items from the other nodes are not synchronized to the new node.
+NOTE: If you join a new node, existing quarantined items from the
+other nodes are not synchronized to the new node.
Deleting Nodes
~~~~~~~~~~~~~~
-Please detach nodes from the cluster network before removing them
-from the cluster configuration. Then run the following command on
-the master node:
+Please detach nodes from the cluster network, before removing them
+from the cluster configuration. Only then you should run the following
+command on the master node:
----
pmgcm delete <cid>
~~~~~~~~~~~~~~~~~
It is highly recommended to use redundant disks on all cluster nodes
-(RAID). So in almost any circumstances you just need to replace the
+(RAID). So in almost any circumstance, you just need to replace the
damaged hardware or disk. {pmg} uses an asynchronous
clustering algorithm, so you just need to reboot the repaired node,
and everything will work again transparently.
-The following scenarios only apply when you really loose the contents
+The following scenarios only apply when you really lose the contents
of the hard disk.
Total Cluster Failure
^^^^^^^^^^^^^^^^^^^^^
-* restore backup (Cluster and node information is not restored, you
+* restore backup (Cluster and node information is not restored; you
have to recreate master and nodes)
* tell it to become master
projects / pmg-docs.git / blobdiff