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Neverfail for SQL ServerFrom STORAGE Magazine
Vol 6, Issue 9 - December 2006 There is certainly no shortage of server fault-tolerant solutions on the market, although many focus primarily on system and component redundancy. Furthermore, they often require identical servers, making them even more costly to implement. Neverfail takes a different approach and can provide fault tolerance at the application level, whilst supporting a range of popular products. Neverfail offers a good selection of modules, including MS Exchange, SharePoint, BlackBerry, Domino, File Server and IIS. Here, we take a look at Neverfail for SQL Server. At its foundation is the Neverfail Heartbeat, which is a single component that provides complete protection for the network, application, data and system environments. It requires a primary and secondary server. However, unlike many solutions, the pair do not need to be identical, making Neverfail more versatile. The operating systems do need to be identical, right down to the service pack and patch level, but you can be more flexible with the hardware. Storage partitions need to be closely matched and, for the network environment, you need at least two NICs in each server. One provides a public interface to present network services and the other is used to create a channel between the servers as a dedicated link for replication. Prior to installation, you must use Neverfail's SCOPE utility with the Lite version taking a snapshot of both systems, including their hardware, software and network bandwidth, and then reporting back on their suitability. SCOPE Professional is worth the extra outlay, as it provides deeper analysis, plus workload monitoring. It's an extremely useful tool that checks whether the servers are compatible partners and will advise on any problems. If critical differences should be discovered, then it won't issue a licence until they are fixed. Installation starts by loading the Heartbeat component on the primary server. Once this has been completed, the routine automatically takes a copy of all required application data and the System State using the Windows Backup utility; also, if required, it can send this direct to a selected location on the secondary server. On the secondary server, you run the same installation utility, which will
restore the backup file to create the same environment as on the primary server.
For testing purposes, we used SQL Server 2000, loaded on the primary system, and
found that Neverfail had migrated the complete application and databases over to
the During normal operations, the primary server provides all network services, with the secondary server maintaining a passive state. Replication starts automatically and can be fully monitored using the Heartbeat management client. This can be run on either server or remotely on another workstation, where it provides a clear picture of the state of the Neverfail components. If the SQL database services on the primary server stop for any reason, Neverfail attempts a restart by default. Alternatively, it can take any corrective action determined by the administrator. In the event of a failure of the primary system, it takes a few seconds to acknowledge this and the secondary server automatically comes into play. If you need to run scheduled maintenance on the primary server, the process can be enforced manually. Called switchover, this takes around 30 seconds to complete, after which the primary system can be closed down, with no further interruption to the application and data services. Neverfail maintains a full log file of all operations, which can be emailed to multiple recipients at scheduled times. During testing, we found Neverfail lived up to its name, handling manual and
automatic failures without any problems. The installation process, it must be
said, is time consuming, but the end result is a slick application failover
environment that is easily customised - and a lot more cost effective than much
of the competition. ST |
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