Docs: Promote DB engine/long-term metrics storage more heavily (#8031)

* Fixes to DOCS home and README

* Edit conf-guide and getting-started

* Add dbengine settings to map

* Fix tutorial and step-by-step

* Fix artifacts of old memory mode types

* A few tweaks

* Push a little harder on README

* Fix for Markos

2 files changed, 8 insertions, 5 deletions

diff --git a/daemon/README.md b/daemon/README.md
index 482265548a..877efd18c2 100644
--- a/daemon/README.md
+++ b/daemon/README.md
@@ -4,9 +4,9 @@
 
 -   You can start Netdata by executing it with `/usr/sbin/netdata` (the installer will also start it).
 
--   You can stop Netdata by killing it with `killall netdata`. You can stop and start Netdata at any point. Netdata
-    saves on exit its round robbin database to `/var/cache/netdata` so that it will continue from where it stopped the
-    last time.
+-   You can stop Netdata by killing it with `killall netdata`. You can stop and start Netdata at any point. When
+    exiting, the [database engine](../database/engine/README.md) saves metrics to `/var/cache/netdata/dbengine/` so that
+    it can continue when started again.
 
 Access to the web site, for all graphs, is by default on port `19999`, so go to:
 
diff --git a/daemon/config/README.md b/daemon/config/README.md
index 720a58f001..4f63f31085 100644
--- a/daemon/config/README.md
+++ b/daemon/config/README.md
@@ -46,7 +46,7 @@ Please note that your data history will be lost if you have modified `history` p
 | glibc malloc arena max for plugins|`1`|See [Virtual memory](../#virtual-memory).|||
 | glibc malloc arena max for Netdata|`1`|See [Virtual memory](../#virtual-memory).|||
 | hostname|auto-detected|The hostname of the computer running Netdata.|||
-| history|`3996`|The number of entries the `netdata` daemon will by default keep in memory for each chart dimension. This setting can also be configured per chart. Check [Memory Requirements](../../database/#database) for more information.|||
+| history|`3996`| Used with `memory mode = save/map/ram/alloc`, not the default `memory mode = dbengine`. This number reflects the number of entries the `netdata` daemon will by default keep in memory for each chart dimension. This setting can also be configured per chart. Check [Memory Requirements](../../database/README.md#database) for more information. |||
 | update every|`1`|The frequency in seconds, for data collection. For more information see [Performance](../../docs/Performance.md#performance).|||
 | config directory|`/etc/netdata`|The directory configuration files are kept.|||
 | stock config directory|`/usr/lib/netdata/conf.d`||||
@@ -56,7 +56,10 @@ Please note that your data history will be lost if you have modified `history` p
 | lib directory|`/var/lib/netdata`|Contains the alarm log and the Netdata instance guid.|||
 | home directory|`/var/cache/netdata`|Contains the db files for the collected metrics|||
 | plugins directory|`"/usr/libexec/netdata/plugins.d" "/etc/netdata/custom-plugins.d"`|The directory plugin programs are kept. This setting supports multiple directories, space separated. If any directory path contains spaces, enclose it in single or double quotes.|||
-| memory mode|`save`|When set to `save` Netdata will save its round robin database on exit and load it on startup. When set to `map` the cache files will be updated in real time (check `man mmap` - do not set this on systems with heavy load or slow disks - the disks will continuously sync the in-memory database of Netdata). When set to `dbengine` it behaves similarly to `map` but with much better disk and memory efficiency, however, with higher overhead. When set to `ram` the round robin database will be temporary and it will be lost when Netdata exits. `none` disables the database at this host. This also disables health monitoring (there cannot be health monitoring without a database). host access prefix||This is used in docker environments where /proc, /sys, etc have to be accessed via another path. You may also have to set SYS_PTRACE capability on the docker for this work. Check [issue 43](https://github.com/netdata/netdata/issues/43).|
+| memory mode         | `dbengine` | `dbengine`: The default for long-term metrics storage with efficient RAM and disk usage. Can be extended with `page cache size` and `dbengine disk space`. <br />`save`: Netdata will save its round robin database on exit and load it on startup. <br />`map`: Cache files will be updated in real-time. Not ideal for systems with high load or slow disks (check `man mmap`). <br />`ram`: The round-robin database will be temporary and it will be lost when Netdata exits. <br />`none`: Disables the database at this host, and disables health monitoring entirely, as that requires a database of metrics. |
+| page cache size     | 32         | Determines the amount of RAM in MiB that is dedicated to caching Netdata metric values. |||
+| dbengine disk space | 256        | Determines the amount of disk space in MiB that is dedicated to storing Netdata metric values and all related metadata describing them |||
+| host access prefix||This is used in docker environments where /proc, /sys, etc have to be accessed via another path. You may also have to set SYS_PTRACE capability on the docker for this work. Check [issue 43](https://github.com/netdata/netdata/issues/43).|
 | memory deduplication (ksm)|`yes`|When set to `yes`, Netdata will offer its in-memory round robin database to kernel same page merging (KSM) for deduplication. For more information check [Memory Deduplication - Kernel Same Page Merging - KSM](../../database/#ksm)|||
 | TZ environment variable|`:/etc/localtime`|Where to find the timezone|||
 | timezone|auto-detected|The timezone retrieved from the environment variable|||