I looove Dokuwiki. It has been my personal notebook for well over a decade. I have 8 MB of text in it, and that only includes the current revisions of pages.

However, I recently started writing my own notebook/wiki because:

I want to convert and write my notes in Markdown so that I can copy and paste snippets between different services easily. I consider Markdown to be the Javascript of the markup syntaxes: it's a long way from the best solution, but it's what the world ended up choosing collectively. When I looked at the code, the whole thing seemed to be tightly coupled to Dokuwiki syntax. It may be possible with some hacking and/or extensions to switch Dokuwiki to Markdown but the same amount of effort could also be spent on just writing a new wiki with only the features I need.

I'm growing increasingly tired of having two scroll bars to deal with whenever I want to edit a page. This can be fixed with templates, probably, but I didn't look too closely into it given the lack of Markdown support.