Just recently, I have received an increased number of telephone calls with regards to running OpenInsight on Virtual Servers (or virtual machines), for example VMware (being the most popular at the moment), Microsoft Virtual PC, etc.
In the main, there are no real technical issues that I am aware of in running OI 8.x and 9.x in these environments and there shouldn’t really be any issues as the virtualisation software ‘should’ take care of sandboxing the server instance and any communications between virtual servers, for disaster recovery etc. That said, Revelation’s testing of these environments is yet to be concluded and, for that reason alone, they remain in the ‘unsupported’ category for the moment.
However, there are OpenInsight licensing questions to be addressed, the answers to which depend greatly on the reasons for the virtualisation, and this is the primary point of this posting.
There are probably more scenarios applicable to this question than those in this article and I will post more details here as they come to light. The three usual reasons that I am asked about though, are covered below:
The days of buying a new server for a new application are over and this appears to be extending to a move away from buying a dedicated application server and a separate data server. Instead, organisations are buying one large and very well resourced server that they then break up into multiple virtual servers. This enables IT staff to sandbox applications, removing the worry about one application or set of data files bumping with another and it also eases the daily backup process. However, one of the main reasons for this move is to tick the green environmental box by reducing the cost of building the server in the first place and, more importantly, in reducing the increasing and ongoing energy costs associated with running several machines compared to one machine.
Sandboxing OpenInsight in this way is perfectly fine. You only have one instance of OpenInsight installed in one place and you are therefore operating within the license.
- Disaster Recovery
Talk to anyone involved with selling virtualisation services, software or hardware and you will quickly find yourself steered into talking about disaster recovery. This appears to be one of the main reasons why IT Managers in larger organisations turn to virtualisation. Again, OpenInsight will usually behave perfectly well in such an environment as (if supported by the virtualisation solution) it is normally the virtualisation software that will handle the communications between the virtual servers to maintain a mirror or whatever the organisation requires to facilitate an automated failover solution. OpenInsight just resides in both places as per any normal installation.However, this scenario usually involves OpenInsight being installed in two or more locations, or a full copy of the software being copied into more than one location. Even though the system is often designed and configured to run only one copy at a time (as a cold spare) and only one is available to end users at any one time, it IS technically a violation of the OpenInsight and Universal Driver licenses. In many situations, duplicate licenses will need to be purchased from Revelation Software, regardless of what the virtualisation salesperson tells you, so I strongly recommend that you contact your usual Revelation representative for clarification on your configuration.That said, Revelation always recommend the Universal Driver Heavy (UDH) as the optimal resource for maintaining a disaster recovery solution for any OpenInsight system. Not least because the UDH provides real time mirroring of Linear Hash files. Whereas, technologies like Microsoft File Replication Services and Volume Shadow copy were designed for periodic replication of static documents. These technologies aren’t capable of, nor optimised to efficiently mirror frequently changing Linear Hash data. A full white paper expanding on the reasons why the UDH 4.6 should be used as the premium solution and the various configuration options will be following over the next few weeks. In the meantime, you can find out more about the UDH on our web site.
- Load Balancing
The use of virtualisation for load balancing is one that I am not over familiar with, but it has come up a couple of times during discussions about OpenInsight and virtualised servers. Furthermore, the issue becomes more complicated as there seem to be many different ways of going about this. For instance, some people have spoken about setting up a system with a shared central engine with processes being spawned on other machines, whilst on other occasions people have talked about load balancing the front end servers each with their own copy of OpenInsight.As I understand it, in most cases the virtualisation solution maintains the virtual servers/machines on one or more physical servers and some other solution (or code) manages the inbound user request and the levels of available resources across the virtualised system. This solution then passes the request to the virtual machine with the most available resources at that time.This scenario, especially where front end application servers are load balanced, often requires multiple copies of OpenInsight to be running in multiple locations. In this instance, there is a clear business benefit where users are accessing (or have access to) each instance of OpenInsight. For this reason, the appropriate number of OpenInsight and Universal Driver licenses must be purchased to cover each instance on each virtual server/machine. Again, I would recommend talking to your usual Revelation representative for clarification on your configuration.
Please remember, if there is any doubt about your proposed installation – call your usual Revelation representative with specific configuration details for clarification of what licenses you will need.