To be able to create a good design, it is imperative to have good requirements for the environment. These requirements must be gathered both at the business and at IT end, as they both have to “use” the platform in the future, although their use will be completely different.
- Where the business has certain availability requirements (e.g. 99.9% 24x7), IT has the requirement that these availability requirements must be achieved using redundancy. The final design has to be an environment design with which all parties can live with.
- In order to deliver a good service, IT will have to be able to test each change to the environment. In order to do this, they will require testing facilities in the form of DTAP environments. In most cases, the business will experience the DTAP strategy as annoying and time consuming.
It is very important that all choices are documented in a design document, especially when the persons performing the implementation are different than the actual administrators of the environment. The design document has to be reviewed and approved by the future administrators before implementation starts. If during implementation a deviation from the original design has to be implemented, this deviation has to be agreed between both parties.
Basically: If the implementation project messes up (for whatever reason), the future administrators will suffer the consequences!!
Very good examples of critical design choices with high impact are:
- Use of a DTAP environment* - During a project, implementing a DTAP strategy requires time and money. Two things a project very often doesn’t have a lot of. Skipping the implementation of DTA environments saves time and money for the project. However this choice will seriously impact administrators in their ability to test changes before implementation (patches/service packs, new solutions or configuration changes).
- Redundancy in the environment - Implementing redundancy requires extra hardware and therefore extra costs for hardware, software licenses and installation. If during implementation the requirements do not include redundancy, this will not be designed and implemented. Unfortunately, adding redundancy later will require a lot of work and has a high impact, especially for SQL Server where adding redundancy (clustering) will mean a complete reinstallation of the entire SQL environment.
- Sizing - I have been part of a project where the available storage was limited. We only had a certain amount of storage available, that was it. The disk space for all servers was just enough to contain all data. Once the environment was transferred to the administrators, one of the first things they had to do was adding extra disk space and moving database across these extra disks.
The message of this story: Most items mentioned might sound obvious, but unfortunately I have seen a lot of situations where this turned out to be harder than you would think/like.
If you are part of the implementation project, make sure that you involve the future administrators as soon as possible. If you are the future administrator, make sure you get involved as soon as possible. Each design decision has to be approved by both parties! So check and communicate between both parties early and continuously.
A very good input for IT requirements are acceptation criteria. This is a list of criteria to which the project has to comply to. That way you can save yourself a huge amount of time, effort and stress! So make sure you create these!
*More on DTAP will follow in a later post