The linked Discord post is also interesting and fun to read. Most of the post is more serious but this is one of the small gems:
> One thing we discovered very quickly was that [world cup] goals scored showed up in our monitoring graphs. This was very cool because not only is it neat to see real-world events show up in your systems, but this gave our team an excuse to watch soccer during meetings. We weren’t “watching soccer during meetings”, we were “proactively monitoring our systems’ performance.”
https://discord.com/blog/how-discord-stores-trillions-of-mes...
It is linked as evidence for Discord using "less than a petabyte" of storage for messages. My best guess is that they multiplied node size and count from this post, which comes out to 708 TB for the old cluster and 648 in the new setup (presumably it also has some space to grow)
yeah we weren't sure about putting that number esp whether it includes all the image attachments, but in any case it's at least around the right reference class for the largest text data operations.