You may want to install a Backup or a DR system on your GN4 system, to mask the effects of a hardware or software failure and to maintain the availability of applications so that the perceived downtime for users is minimized.

The purpose

The purpose is an instant or a short-delayed switch to a secondary system in case of the failure of the primary system. See Hot or Warm? to learn about the differences and limitations of an instant and a short-delayed switch.

Basic methods

There are many methods to set up a valid secondary system, from the software solutions such as VMWare, VMotion and similar, clustering, simple data and database backup on secondary servers, etc. The efficiency and cost of such methods is proportionally related: the most efficient secondary system is very costly; the low-cost secondary system has lower efficiency.

Difference between a Backup and a DR secondary systems

The main difference between a Backup GN4 system and a DR GN4 system, is the physical location: a backup secondary system is typically built on the same site as the primary system, while a DR secondary system is surely built on another site and another physical location, possibly rather distant.

The most important consequence is that for the backup GN4 system you may safely rely on a huge bandwidth and very fast syncing operations typical for LAN connections, while the DR GN4 system may suffer of the lower bandwidth and therefore slower syncing operations typical for WAN connections.

Moreover, the LAN based secondary system can easily be isolated through switches and therefore the bandwidth of the main communication channel (also with the remote offices) is fully preserved. That is quite different when you come down to the WAN based DR system: while you can still isolate it through switches, unless you have a separate communication line for the DR purposes (which is often not the case), the syncing operations will steal bandwidth and therefore reduce the performances of the remote offices and connections even when connected to the primary system,

By all other means, the requirements of a DR system are practically equal to those of the Backup system.

Basic GN4 related needs

The basic GN4 needs related to backup and to disaster recovery are:

1.The GN4 database has to be replicated/mirrored on a secondary SQL server or cluster, so you can switch to that server/cluster in case of the failure of the primary SQL server.

2.The IIS server(s) need to have the backup instances, so you can switch on that/those servers in case of the failure of the primary IIS server(s).

3.The Back4 server(s) need to have the backup instances, so you can switch on that/those servers in case of the failure of the primary Back4 server(s).

4.The indexing server(s) (Exalead) need to have the backup instances, so you can switch on that/those servers in case of the failure of the primary server(s).

5.The third-party services, e.g. Wire news provider (their downloader software or FTP access), E-mail server (for GN4 to download and to send e-mails), public web access (for the users connecting from outside), Active directory (for services relying on it).

6.The data in GN4 volumes has to be replicated/mirrored on more than one storage.

7.A set of procedures has to be put in place to switch to another set of servers, making changes in configurations, paths and URLS to access.