Which OS Is Right for you?
In this article we will take a brief look at what separates the 2 versions of NetApp’s OnTap Operating systems. Let’s start first with the older of the 2, 7 mode:
7-Mode is NetApp’s legacy ONTAP OS. While it is still supported on most filers, it is not supported on newer filers like the 8000 series (or newer) and 2500 series (or newer). 7-mode will eventually be phased out NetApp has stated that the current rev will be the last. The limitation of 7-mode is its capacity of only 2 controllers per cluster. This is ideal if you have a small, 2 controller cluster, but hardly a good solution if your data requirements are complex, and you have several systems that need to be clustered.
Clustered Data ONTAP (CDOT)
As you may already figured that out from the name itself, c-mode gives much better scaling options. As you can see, 7-mode normally is configured in 2-node High availability. cDOT is also configured into HA pairs, however within cDOT you can connect up to 12 pairs (NAS configuration) or up to 4 pairs (SAN configuration) in one cluster. If a problem arises with one filer, you are able to pull that filer out of the cluster, fix it, and put it back into the cluster and still maintain your uptime.
Should you upgrade to CDOT?
Upgrading to cDOT can get expensive, and complex. If the performance of your current system is adequate performance-wise and reliable, then it’s probably best to stay with 7-Mode for the time being. If you find that you have a need for more filers in your cluster, and your current system is underperforming, then it is time to take look at what an upgrade would look like for your environment.