The forum I run currently has 326,955 threads and 7,518,307 posts.

--RayJ

You'll probably find that there is (or has been) an issue with the post table, when a repair was attempted it failed and left an unfinished temp file behind which you need to delete prior to repairing again then all will be good!, you'll need to use ssh to find the postindex.TMD file and delete it, when a file is attempting to repair they make another temporary file, if the databse crashes for some reason when this is taking place it leaves that file unfinished, trying to repair again does nothing as that file still exists, i suggest you backup your postindex table as it is then via ssh find that file, delete it, and repair again, you could run the Check table or analyse table first, when you see the full text it will give you the name of the file that already exists.

No there isn't any such issue. With the Niche my forum is in, alot of content goes into each post, thanks though.

I'm running forum with:

Threads: 415,471
Posts: 11,706,710
Members: 181,871

In my old web hosting, crash once or twice every 1-2 month, but quick repair always fix the problem.

After moving to other web hosting with new configuration, already running for 2 month and never have any database issue.