That will depend on usage. If you subscribe to a lot of communities that are very active the database will grow fairly fast. If your users post a ton of large files then that will grow much much faster than the database. Your instance also caches image thumbnails so that can grow somewhat fast too.

Currently sitting at 750 MB for pictrs and 500MB for postgres after a week, so you may want to plan a decent size but 30-40GB should be fine for a while to get started. Add some monitoring for when it reaches 10, 20 and 30GB and keep an eye on it.

Do you need Mastodon, or can it be something similar? Mastodon does a lot of caching. For my single-user instance I run Akkoma, which is very leight-weight and has all (even more) features Mastodon has.

@Solvena my kbin instance is using 37 GB right now, and it is one of the oldest instances. I don't have many user thou.

My Lemmy instance is using 3GB and it has 100 users.

No expert here but usualy you use an external object storage (should be configurable in lemmy via pict-rs) which should be cheaper then VPS storage ^^

Maybe have a look into it.

I can't help with Lemmy, but I've been running a single-user Mastodon instance for almost a year now.

Like you, I found that the media very quickly used up much more disk space than I anticipated. There are a few things you can do.

You can tune how long media is stored for: some of this is done in the admin interface, but really you need to set up cron jobs to regularly run various tootctl commands. This is the crontab I use:

SHELL=/bin/bash
PATH=/home/mastodon/.rbenv/shims:/home/mastodon/.rbenv/bin:/usr/local/bin:/usr/bin:/bin

RAILS_ENV=production
# Remove media attachments older than 8 days
11  19  *   *   *     cd /home/mastodon/live && time bin/tootctl media remove --days 8
# Remove link previews older than 28 days
22  5   *   *   *     cd /home/mastodon/live && time bin/tootctl preview_cards remove --days 28
# Remove files not linked to any post
 3  23  *   *   0     cd /home/mastodon/live && time bin/tootctl media remove-orphans
# Prune remote accounts that never interacted with a local user
44  1   *   *   *     cd /home/mastodon/live && time bin/tootctl accounts prune

You can of course choose even stricter settings but I found that no matter what I did, given that I am following approx 1,000 other Fediverse accounts it still used up more disk space than I was comfortable with.

So I offloaded most of the media storage onto an S3-compatible service. It's breaking the self-hosting ethos somewhat, but with Backblaze B2 I can happily store and serve several hundred GB of media files for just a couple of dollars a month. To me, that was a no-brainer.

Will there be some sort of OS running on this VPS like Ubuntu, Debian etc.? The folder my Lemmy instance is stored in is 117 MB big. I have 1 user and follow 23 communities.

With Lemmy, it will depend more on the amount of media that your users upload than anything. With Mastodon, you also will have to consider the amount of data in the cache.

With Mastodon, I have (small) instances running for about an year or so which are using less than 100GB, and I have instances from power users that went on to take ~250GB in less than a month.

You can set up Mastodon to delete posts after a certain age and to clear the remote cache periodically. This would help mitigate both things.

I have my lemmy instance currently using about 2 GB space, I'm going to set up Mastadon this weekend I hope. There are cheap smaller dedicated servers from kimsufi for like $10 with 1/2 TB HDD.

Also Hetzner cloud has compute and disk separated, so you can scale one or the other.

I've got a 500GBSSD box from Hetzner, but I'm also hosting other things there and dropped VMs from Linode I had previously and consolidated there.

You could use object storage, like s3 or wasabi, for lemmy picture/media storage, if that's eating up most space. "cloud" providers are bit bananas when you need more disk, at one point its cheaper to go down a dedicated route. Depends on your budget..

Edit: Others might chime in with a better answer, at the moment bot sure what your budget is, so its bit of assumptions from my side.

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