* Clustering features in NetWare 6.5
We’re continuing our look at the additional NetWare features that will appear in NetWare 6.5, due to ship in June and today I want to talk about clustering.
Novell Cluster Services was introduced as a high availability option soon after the release of NetWare 5. It was the logical follow-on to the System Fault Tolerance (SFT III) option that was introduced with NetWare 3 and NetWare 4. It allowed for mirrored server hardware – two, usually identical, servers either of which could run the network should one experience a hardware failure.
As hardware became more reliable and as software became more complicated the SFT III solution became less desirable. A software failure would quickly bring down both servers in a mirrored pair, leaving you with no server on the network and facing a long process of correcting the problem.
Clustered servers, on the other hand, do not mirror each other during operation so that a software or hardware failure on one does not mean the network grinds to a halt. Instead, another server (could be more than one other server) in the cluster takes over the operations performed by the failed server which the network manager has deemed necessary to continue nonstop.
Cluster services was initially only available from vendors who installed it on the hardware before selling it to you. Eventually, it became available as a “software only” purchase, and NetWare 6.0 shipped with a license for a two server cluster which you could set up on your own.
NetWare 6.5 introduces two major changes. First, the included license covers up to 32 clustered servers. Since your server license allows you to install as many NetWare 6.5 servers as you’d like, it made little sense to limit the number that could be included in the cluster. Second, NetWare 6.5 will support the new iSCSI standard for connecting the shared disk storage needed for cluster services.
The introduction of iSCSI connectivity is important for two reasons. Previously, Fiber Channel connections were necessary for the shared disks in a cluster. Fiber Channel is expensive (compared to Ethernet) and has a distance limitation that almost requires all shared disks to be in one room. ISCSI eliminates both of these problems by transmitting SCSI commands over the IP network using standard Ethernet cards and cables. In theory, the disks in an iSCSI storage-area network could be on different continents. Now that’s fault tolerance.
Read more about Novell’s cluster services at https://www.novell.com/products/clusters/ncs/ and start planning a truly fault tolerant network based on NetWare 6.5.
