Tenboro should have had a backup plan for years, yes, but it seems like he doesn't care to continue any further. This notice was abrupt by the web host, which wouldn't have allowed for much to happen
in this specific instance.
Splitting the website, however, wouldn't have done anything irrespective of the logistical nightmare. It sounds like the hosting company was scared off by loli/shota even though none of the laws have changed and it's not illegal in Netherlands (as, obviously, it's not cheese pizza -- anyone with a brain can divorce fiction from reality). The whole exact reason is fuzzy but not super pivotal since the company's actions would almost always be the same. Genres don't help with that, and the cause can change (e.g. one day it might be even stricter copyright enforcement).
Whatever database that exists is probably no higher than 100 TB despite the approximate petabyte figure being thrown about, based on
site statistics and a direct quote indicating that gallery images alone were above 50 TB. Different resolutions would pad that figure, of course, so this is a guess.
Let's hope that he is able to hold his word re: releasing a mirror of the data, and that the other staff or anons can step up to the plate for a replacement website. It's a tough job.
For our part, the best we can do is
backup galleries -- using high resolution, if affordable in bandwidth and storage -- and
take notes for later, e.g. recommendations. Unfortunately, I think 75% of my favorites are gone due to "forbidden content" being more than just shota/loli and incorrectly applied tags...though I do happen to buy favorites from DLSite occasionally, so there's that.
They put a Wiki section about this overall fiasco, btw -
https://ehwiki.org/wiki/Site_Retirement
Nyaa has several metadata torrents, which is also a decent start even if incomplete. We need both the galleries and metadata backed up.
Edit: Torrenting is another good proactive option w/o a website, additional trackers will help -
https://forums.e-hentai.org/index.php?showtopic=229534