Cohesion & Coupling: Bundling applications together in a single MSI file, may seem like a
good idea. It seems intuitively nice and simple. However, speaking
from real world experience I almost always end up splitting
applications to install via their own MSI files, and I don't like
multi-lingual setups either (true multi-lingual setups are difficult because translated content is typically not ready when marketing and sales push to release the native language version quickly - typically the English version).
The only time it is really safe to deploy applications together is when they are guaranteed to:
- Always be used together by end users
- Always get updated at the same time
- Won't grow substantially in size over time (
Localization, New Prerequisites, etc...)
And normally it is impossible to predict any of this. Typically you will get new requirements quickly.
Central Challenge: What will likely take on a release-cycle of its own? (split it right now). Things tend to happen suddenly! Here are some common challenges:
Bug fixes: if only one application has a bug, management will want to deliver only one new MSI and leave application 2 untouched and without the need to do a whole new QA-run for both applications after install. This is to reduce risk and to deliver a smaller update that is also quicker to test and verify. Patching is very complicated, and generally safer for MSI files that are as simple as possible without too many languages, custom actions or GUI constructs.
Localization: suddenly you get a requirement to make application 1 available in Italian, application 2 does not need to be translated. Language support tends to greatly increase the complexity of a setup, not to mention the size of it. Your "nice and simple" MSI has now suddenly gotten complicated to maintain, and sluggish to build. It is also a real pain if you need a single setup, and you translate it in many languages - you won't be able to compile the RTM version until all the language updates are in. I can tell you right now that marketing / sales people will have no concept of holding back the English version until all localized versions are ready.
QA / UAT: if the applications are large, delivering 2 separate MSI files will make it easier to split the testing effort between different QA teams and to deliver new updates via nightly builds etc...
Release schedule: suddenly the release schedule for the applications change - application 1 is now updated every month, whilst application 2 is updated only every six months. If different users use the applications, how do you deliver updates? Build it all in one MSI and give it a new version number only to have application 2 users install the same application over again?
Apply the overall developer principles of cohesion and coupling to deployment packages, and you will save yourself a lot of trouble. If the applications now OR in the future may take on their own life cycle - split their deployment right away. And who can see into the future?
Please note that you generally will wrap multiple MSI files in a bootstrapper so that users still have only one file to relate to, even if the products are installed via separate MSI files.
Wix update: With the advent of Wix to create complex setups it has become easier to build Wix include files that can be compiled into several MSI files. This effectively becomes a more flexible type of merge module. This may simplify the splitting or merging of MSI files in the future. See a discussion of this feature here. One more link.
Sheer setup size: There are some limitations with regards to how many components and files you can have in a single MSI. Some details:
It can be helpful to "decompose" a huge MSI into several related MSI for this reason and other reasons listed above - in order to make maintenance easier (build and compile speed, rebuild of just one of many MSI files, etc...). Finally you should stick to using a single file per component to make upgrading and patching work properly. Several MSI files can be installed in sequence using bootstrappers or launcher applications such as Burn from WiX, or features in commercial tools such as Installshield and Advanced Installer. Here is an answer which touches on this topic. And just trowing in another answer which is a little bit similar.
Links:
