[docs] Update system requirements, move things around a bit (#3157)

docs/getting_started/index.md

@@ -8,62 +8,50 @@ Before deploying GoToSocial, it's important to think through a few things as som
     
     In that same vein, if you already have another ActivityPub implementation running on example.org you should not attempt to switch to GoToSocial on that domain.
 
-## Database
-
-GoToSocial supports both SQLite and Postgres and you can start using either. We do not currently have tooling to support migrating from SQLite to Postgres or vice-versa, but it is possible in theory.
-
-For databases to perform properly, they should be run on fast storage that operates with low and stable latency. It is possible to run databases on network attached storage, but this adds variable latency and network congestion to the mix, as well as potential I/O contention on the origin storage.
-
-!!! danger "Cloud Storage Volumes"
-    Not all cloud VPS storage offerings are equal, and just because something claims to be backed by an SSD doesn't mean that it will necessarily be suitable to run a GoToSocial instance on. Please see the [Server/VPS section](#vps) section below.
-
-SQLite is great for a single-user instance. If you're planning on hosting multiple people it's advisable to use Postgres instead. You can always use Postgres regardless of the instance size.
-
-!!! tip
-    Please [backup  your database](../admin/backup_and_restore.md). The database contains encryption keys for the instance and any user accounts. You won't be able to federate again from the same domain if you lose these keys.
-
-## Domain name
-
-In order to federate with others, you'll need a domain like `example.org`. You can register your domain name through any domain registrar, like [Namecheap](https://www.namecheap.com/). Make sure you pick a registrar that also lets you manage DNS entries, so you can point your domain to the IP of the server that's running your GoToSocial instance.
-
-You'll commonly see usernames existing at the apex of the domain, for example `@me@example.org` but this is not required. It's perfectly fine to have users exist on `@me@social.example.org` instead. Many people prefer to have usernames on the apex as its shorter to type, but you can use any (subdomain) you control.
-
-It is possible to have usernames like `@me@example.org` but have GoToSocial running on `social.example.org` instead. This is done by distinguishing between the API domain, called the "host", and the domain used for usernames, called the "account domain".
-
-If you intend to deploy your GoToSocial instance in this way, please read the [Split-domain deployments](../advanced/host-account-domain.md) document for details on how to do this.
-
-!!! danger
-    It's not possible to safely change whether the host and account domain are different after the fact. It requires regenerating the database and will cause confusion for any server you have already federated with. Once your instance host and account domain are set, they're set.
-
-## TLS
-
-For federation to work, you have to use TLS. Most implementations, including GoToSocial, will generally refuse to federate over unencrypted transports.
-
-GoToSocial comes with built-in support for provisioning certificates through Lets Encrypt. It can also load certificates from disk. If you have a reverse-proxy in front of GoToSocial you can handle TLS at that level instead.
-
-!!! tip
-    Make sure you configure the use of modern versions of TLS, TLSv1.2 and higher, in order to keep communications between servers and clients safe. When GoToSocial handles TLS termination this is done automatically for you. If you have a reverse-proxy in use, use the [Mozilla SSL Configuration Generator](https://ssl-config.mozilla.org/).
-
 ## Server / VPS System Requirements
 
-!!! warning "Clustering / multi-node deployments"
-    GoToSocial does not support [clustering or any form of multi-node deployment](https://github.com/superseriousbusiness/gotosocial/issues/1749). Though multiple GtS instances can use the same Postgres database and either shared local storage or the same object bucket, GtS relies on a lot of internal caching to keep things fast. There is no mechanism for synchronising these caches between instances. Without it, you'll get all kinds of odd and inconsistent behaviour.
+GoToSocial aims to fit in small spaces so we try and ensure that the system requirements are reasonably minimal, while still providing the functionality that people expect of a social media server.
 
-GoToSocial aims to fit in small spaces so we try and ensure that the system requirements are fairly minimal.
+You can find more detail on system requirements below, but in short you should aim to have a system with at least **1 CPU core**, about **1GB of memory** (maybe more depending on your operating system), and **15GB-20GB of storage space** (for the first few years).
 
 ### Memory
 
-For a single-user instance with about 100-300 followers/followees, GoToSocial will likely hover consistently between 100MB to 250MB of RAM usage once the internal caches are hydrated.
+**Tl;dr -- 1GB of total RAM on your system should be enough, but you may be able to get away with 512MB.**
 
-RAM usage may temporarily spike higher during periods of load (for example, when a status gets boosted by someone with many followers), so you should account for some overhead.
+For a small instance (1-20 active users), GoToSocial will likely hover consistently between 250MB and 350MB of RAM usage once the internal caches are hydrated:
 
-512MB to 1GB of total RAM should be enough.
+![Grafana graph showing GoToSocial heap in use hovering around 300MB and spiking occasionally to 400MB-500MB.](../assets/getting-started-memory-graph.png)
 
-In memory constrained environments, you can try setting `cache.memory-target` to a value lower than the default 100MB (see the database configuration options [here](../configuration/database.md#settings)).
+In the graph above you can see that RAM usage spikes during periods of load. This happens, for example, when when a status gets boosted by someone with many followers, or when the embedded `ffmpeg` binary is decoding or reencoding media files into thumbnails (especially larger video files).
+
+You should account for some overhead in this case, and if necessary [configure some swap memory](#swap).
+
+!!! tip
+    In memory constrained environments, you can also try setting `cache.memory-target` to a value lower than the default 100MB (see the database configuration options [here](../configuration/database.md#settings)). 50MB has been shown to work fine.
+
+    This should make the overall memory use a little lower once the internal caches are hydrated, but at the cost of slightly higher latency on some requests, as GtS will need to call the database more frequently.
+
+!!! info "Why does `htop` show higher memory usage than in the graph?"
+    You may find that if you run `top` or `htop` or some other system resource readout tool on your server, GoToSocial shows higher reserved memory than in the graph above. However, this does not always reflect actual *in-use* memory by GoToSocial. This disparity is caused by the fact that the Go runtime releases memory back to the operating system somewhat conservatively, since it is often cheaper to hold on to idle memory in order to reuse it, than it is to immediately release it back to the OS and have to ask for it back later on.
 
 ### CPU
 
-CPU usage is only intensive when handling media (encoding blurhashes, mostly) and/or handling a lot of federation requests at the same time. 1 decent CPU core should be fine.
+**Tl;dr -- 1 decent CPU core should be fine.**
+
+CPU usage is only intensive when handling media (encoding blurhashes, mostly) and/or handling a lot of federation requests at the same time. As long as you're not running CPU intensive stuff on the same machine, 1 CPU core will do the job.
+
+### Storage
+
+**Tl;dr -- 15GB-20GB of available storage space should be fine for a few years.**
+
+GoToSocial uses storage for its database files, and for storing + serving media files like avatars, attachments, etc., though you can [configure GtS to use an S3 bucket for media instead](../configuration/storage.md) if you prefer.
+
+After about 3 years of use for a single-user instance, following ~300 people, you can expect your sqlite.db file or Postgres database volume to get up to around 10GB or so.
+
+For media storage, including [storage of remote media files in the cache](../admin/media_caching.md), you should budget about 5GB-10GB of space. GoToSocial automatically cleans up after itself by removing unused remote media from the cache after a while. If storage space an issue, you can [tune this media cleanup behavior](../admin/media_caching.md#cleanup) to clean more regularly and/or to keep remote media cached for less time.
+
+!!! info
+    Don't be alarmed if your sqlite.db file or your Postgres volume grows very quickly at first, this is normal. When you first deploy your instance and start federating, your instance discovers and stores accounts and statuses from other instances rapidly. However, this will gradually slow down the longer your instance is deployed, as you naturally start to see fewer "new" accounts (ie., accounts that your instance hasn't seen yet, and therefore hasn't yet stored in the database).
 
 ### Single-board Computers
 
@@ -105,6 +93,44 @@ The BSD family of distributions don't document memory requirements as much, but
 [rhelreq]: https://access.redhat.com/articles/rhel-limits#minimum-required-memory-3
 [fedorareq]: https://docs.fedoraproject.org/en-US/fedora/latest/release-notes/welcome/Hardware_Overview/#hardware_overview-specs
 
+## Database
+
+GoToSocial supports both SQLite and Postgres as database drivers. Though it is possible in theory to swap your database from SQLite to Postgres or vice versa, we do not currently have tooling to support this, so you should consider your choice of database carefully when starting out.
+
+SQLite is the default driver and it's been shown to work brilliantly for instances in the range of 1-30 users (or maybe more).
+
+If you're planning on hosting more people than this on an instance, you may wish to use Postgres instead, as it offers the possibility of database clustering and redundancy, at the cost of some complexity.
+
+Regardless of which database driver you choose, for proper performance they should be run on fast storage that operates with low and stable latency. It is possible to run databases on network attached storage, but this adds variable latency and network congestion to the mix, as well as potential I/O contention on the origin storage.
+
+!!! danger "Cloud Storage Volumes"
+    Not all cloud VPS storage offerings are equal, and just because something claims to be backed by an SSD doesn't mean that it will necessarily be suitable to run a GoToSocial instance on. Please see the [Server/VPS section](#vps) section below.
+
+!!! tip
+    Please [backup your database](../admin/backup_and_restore.md). The database contains encryption keys for the instance and any user accounts. You won't be able to federate again from the same domain if you lose these keys!
+
+## Domain name
+
+In order to federate with others, you'll need a domain like `example.org`. You can register your domain name through any domain registrar, like [Namecheap](https://www.namecheap.com/). Make sure you pick a registrar that also lets you manage DNS entries, so you can point your domain to the IP of the server that's running your GoToSocial instance.
+
+You'll commonly see usernames existing at the apex of the domain, for example `@me@example.org` but this is not required. It's perfectly fine to have users exist on `@me@social.example.org` instead. Many people prefer to have usernames on the apex as its shorter to type, but you can use any (subdomain) you control.
+
+It is possible to have usernames like `@me@example.org` but have GoToSocial running on `social.example.org` instead. This is done by distinguishing between the API domain, called the "host", and the domain used for usernames, called the "account domain".
+
+If you intend to deploy your GoToSocial instance in this way, please read the [Split-domain deployments](../advanced/host-account-domain.md) document for details on how to do this.
+
+!!! danger
+    It's not possible to safely change whether the host and account domain are different after the fact. It requires regenerating the database and will cause confusion for any server you have already federated with. Once your instance host and account domain are set, they're set.
+
+## TLS
+
+For federation to work, you have to use TLS. Most implementations, including GoToSocial, will generally refuse to federate over unencrypted transports.
+
+GoToSocial comes with built-in support for provisioning certificates through Lets Encrypt. It can also load certificates from disk. If you have a reverse-proxy in front of GoToSocial you can handle TLS at that level instead.
+
+!!! tip
+    Make sure you configure the use of modern versions of TLS, TLSv1.2 and higher, in order to keep communications between servers and clients safe. When GoToSocial handles TLS termination this is done automatically for you. If you have a reverse-proxy in use, use the [Mozilla SSL Configuration Generator](https://ssl-config.mozilla.org/).
+
 ## Ports
 
 GoToSocial needs ports `80` and `443` open.
@@ -117,17 +143,18 @@ If you can't leave `443` and `80` open on the machine, don't worry! You can conf
 !!! tip
     You should configure a firewall on your machine, as well as some protection against brute-force SSH login attempts and the like. Take a look at our [firewall documentation](../advanced/security/firewall.md) for pointers on what to configure and tools that can help you out.
 
+## Clustering / multi-node deployments
+
+GoToSocial does not support [clustering or any form of multi-node deployment](https://github.com/superseriousbusiness/gotosocial/issues/1749).
+
+Though multiple GtS instances can use the same Postgres database and either shared local storage or the same object bucket, GtS relies on a lot of internal caching to keep things fast. There is no mechanism for synchronising these caches between instances. Without it, you'll get all kinds of odd and inconsistent behaviour. Don't do this!
+
 ## Tuning
 
 Aside from the many instance tuning options present in the [example config file](https://github.com/superseriousbusiness/gotosocial/blob/main/example/config.yaml) you can do additional tuning on the machine your GoToSocial instance is running on.
 
 ### Swap
 
-It is possible to run a system without swap. In order to safely do so and ensure consistent performance and service availability, you need to tune the kernel, system and your workloads accordingly. This requires a good understanding of your kernel's memory management system as well as the memory usage patterns of the workloads you're running.
-
-!!! note
-    Swap is used to ensure the kernel can efficiently reclaim memory. This is useful even when a system is not experiencing memory contention, like freeing up memory that was only used during process startup. This allows more things that are actively used to be cached in memory. Swap is not what makes your application slow. Experiencing memory contention is what makes things slow.
-
 Unless you're experienced in doing this kind of tuning and troubleshooting the issues that may arise from not having swap, you should follow your distribution or hosting provider's recommendations and configure an appropriate amount of swap. If your distribution or hosting provider doesn't provide guidance, you can use the following rule of thumb for a server:
 
 * less than 2GB of RAM: swap = RAM × 2
@@ -138,6 +165,11 @@ Unless you're experienced in doing this kind of tuning and troubleshooting the i
     
     By default it's `60`. You can lower that to `10` for starters and keep an eye out. It's possible to run with even lower values, but it's likely unnecessary. To make the value persistent, you'll need to drop a configuration file in `/etc/sysctl.d/`.
 
+While it is possible to run a system without swap, in order to safely do so and ensure consistent performance and service availability, you need to tune the kernel, system and your workloads accordingly. This requires a good understanding of your kernel's memory management system as well as the memory usage patterns of the workloads you're running.
+
+!!! note
+    Swap is used to ensure the kernel can efficiently reclaim memory. This is useful even when a system is not experiencing memory contention, like freeing up memory that was only used during process startup. This allows more things that are actively used to be cached in memory. Swap is not what makes your application slow. Experiencing memory contention is what makes things slow.
+
 [sysctl]: https://man7.org/linux/man-pages/man8/sysctl.8.html
 
 ### Memory and CPU limits