When changing platforms, how can existing content be handled in a non-disruptive manner?

Question

In considering migrating to a new platform, what considerations should be made in regard to existing content? This move is needed to due various reasons (pick something...needed features, integration with the outside world, host migration that doesn't support the existing platform, etc.)

As an example, when migrating from one forum software to another a community has multiple options on how to deal with old content. One option is to migrate it all content (posts, users, groups, private messages, etc) to the new platform. This is not entirely reliable as my experience has shown that user groups and permissions rarely migrate successfully if you have somewhat complicated permissions. This leaves the brand new forum in a semi-functional state.

Another option is to close the old board and prevent new posts and members. Leave a link to this place as an archive, but force new content to be created on the new board. The disadvantage here (from a user's perspective) is that everyone is starting fresh. Members that have years in the community suddenly have post counts equal to that one guy that registered yesterday.

Obviously the community doesn't want to lose this old content, but they don't want to migrate to something that doesn't work either. How can a migration be handled successfully without losing existing data?

Answer 1

Option 1 is "nice; expensive". It's rarely easy and often would require a lot of manual work to fill in gaps where the two databases don't overlap. If you can take it without too much effort, take it. If it would bog the resources (esp. human resources) unreasonably, for extended period of time, skip it.

Option 2 is "easy; cheap", the cost of running the old platform in "archive mode" is usually minimal, and you can always scrap it entirely in a couple years.

What you should definitely do if you take option 2 though, is first, deleting all sensitive information like user passwords, or more personal entries, and then making pretty sure the site is really read-only (say, making the database file read-only). Just disabling forms on the WWW could easily turn the old site into spam-infested bot playground, or worm-spreading infection nest. Make sure you are still able to temporarily revert it to "writable" by moderators - sometimes a quitting user may demand all their content deleted, or someone finds given old post is violating copyright or constitutes slander, and then you'll be required to delete these. These are cases rare enough though, that keeping the site "writable" at all times poses a security risk - considering you're unlikely to maintain (=patch) the old platform you should assume it is possible it will be hacked and compromised - just make sure the attacker will not gain anything that way.

Answer 2

The first option is almost always the better option, even if it requires re setting up your permissions. Some forum software allows you to disable posting and viewing of the board until you get set up.

Considering the amount of downtime you will need to get migrated and set up is needed. At least an estimate can help ("when we're done" sounds really unhelpful).

There also may be a learning curve to using a new system (for the moderators and users) if the system is very different than the one you are currently using.