Configuring Backup Hosts and Connections

You use vbr to back up your database to one or more hosts (known as backup hosts) that can be outside of your database cluster.

You can use one or more backup hosts or a single S3 bucket to back up your database. Use the vbr configuration file to specify which backup host each node in your cluster should use.

Before you back up to hosts outside of the local cluster, configure the target backup locations to work with vbr. The backup hosts you use must:

  • Have sufficient backup disk space.
  • Be accessible from your database cluster through SSH.
  • Have passwordless SSH access for the Database Administrator account.
  • Have either the Vertica rpm or Python 3.7 and rsync 3.0.5 or later installed.
  • If you are using a stateful firewall, configure your tcp_keepalive_time and tcp_keepalive_intvl sysctl settings to use values less than your firewall timeout value.

Configuring TCP Forwarding on Database Hosts

vbr depends on TCP forwarding to forward connections from database hosts to backup hosts. For copycluster and replication tasks, you must enable TCP forwarding on both sets of hosts. SSH connections to backup hosts do not require SSH forwarding.

If it is not already set by default, set AllowTcpForwarding = Yes in /etc/ssh/sshd_config and then send a SIGHUP signal to sshd on each host. See the Linux sshd documentation for more information.

If TCP forwarding is not enabled, tasks requiring it fail with the following message: "Errors connecting to remote hosts: Check SSH settings, and that the same Vertica version is installed on all nodes."

On a single-node cluster, vbr uses a random high-number port to create a local ssh tunnel. This fails if PermitOpen is set to restrict the port. Comment out the PermitOpen line in sshd_config.

Creating Configuration Files for Backup Hosts

Create separate configuration files for full or object-level backups, using distinct names for each configuration file. Also, use the same node, backup host, and directory location pairs. Specify different backup directory locations for each database.

For optimal network performance when creating a backup, Vertica recommends that you give each node in the cluster its own dedicated backup host.

Preparing Backup Host Directories

Before vbr can back up a database, you must prepare the target backup directory. Run vbr with a task type of init to create the necessary manifests for the backup process. You need to perform the init process only once. After that, Vertica maintains the manifests automatically.

Estimating Backup Host Disk Requirements

Wherever you plan to save data backups, consider the disk requirements for historical backups at your site. Also, if you use more than one archive, multiple archives potentially require more disk space. Vertica recommends that each backup host have space for at least twice the database node footprint size. Follow this recommendation regardless of the specifics of your site's backup schedule and retention requirements.

To estimate the database size, use the used_bytes column of the storage_containers system table as in the following example: 

=> SELECT SUM(used_bytes) FROM storage_containers WHERE node_name='v_mydb_node0001'; 
total_size 
------------
  302135743
(1 row)

Making Backup Hosts Accessible

You must verify that any firewalls between the source database nodes and the target backup hosts allow connections for SSH and rsync on port 50000.

The backup hosts must be running identical versions of rsync and Python as those supplied in the Vertica installation package.

Setting Up Passwordless SSH Access

For vbr to access a backup host, the database superuser must meet two requirements:

  • Have an account on each backup host, with write permissions to the backup directory.
  • Have passwordless SSH access from each database cluster host to the corresponding backup host.

How you fulfill these requirements depends on your platform and infrastructure.

SSH access among the backup hosts and access from the backup host to the database node is not necessary.

If your site does not use a centralized login system (such as LDAP), you can usually add a user with the useradd command or through a GUI administration tool. See the documentation for your Linux distribution for details.

If your platform supports it, you can enable passwordless SSH logins using the ssh-copy-id command to copy a database administrator's SSH identity file to the backup location from one of your database nodes. For example, to copy the SSH identity file from a node to a backup host named backup01:

$ ssh-copy-id -i dbadmin@backup01|
Password:

Try logging into the machine with "ssh dbadmin@backup01". Then, check the contents of the ~/.ssh/authorized_keysfile to verify that you have not added extra keys that you did not intend to include. 

$ ssh backup01 
Last login: Mon May 23 11:44:23 2011 from host01

Repeat the steps to copy a database administrator's SSH identity to all backup hosts you use to back up your database.

After copying a database administrator's SSH identity, you should be able to log in to the backup host from any of the nodes in the cluster without being prompted for a password.

Increasing the SSH Maximum Connection Settings for a Backup Host

If your configuration requires backing up multiple nodes to one backup host (n:1), increase the number of concurrent SSH connections to the SSH daemon (sshd). By default, the number of concurrent SSH connections on each host is 10, as set in the sshd_config file with the MaxStartups keyword. The MaxStartups value for each backup host should be greater than the total number of hosts being backed up to this backup host. For more information on configuring MaxStartups, refer to the man page for that parameter.

See Also