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diff --git a/docs/guides/longer-metrics-storage.md b/docs/guides/longer-metrics-storage.md new file mode 100644 index 000000000..85b397f6d --- /dev/null +++ b/docs/guides/longer-metrics-storage.md @@ -0,0 +1,160 @@ +<!-- +title: "Change how long Netdata stores metrics" +description: "With a single configuration change, the Netdata Agent can store days, weeks, or months of metrics at its famous per-second granularity." +custom_edit_url: https://github.com/netdata/netdata/edit/master/docs/guides/longer-metrics-storage.md +--> + +# Change how long Netdata stores metrics + +Netdata helps you collect thousands of system and application metrics every second, but what about storing them for the +long term? + +Many people think Netdata can only store about an hour's worth of real-time metrics, but that's simply not true any +more. With the right settings, Netdata is quite capable of efficiently storing hours or days worth of historical, +per-second metrics without having to rely on an [exporting engine](/docs/export/external-databases.md). + +This guide gives two options for configuring Netdata to store more metrics. **We recommend the default [database +engine](#using-the-database-engine)**, but you can stick with or switch to the round-robin database if you prefer. + +Let's get started. + +## Using the database engine + +The database engine uses RAM to store recent metrics while also using a "spill to disk" feature that takes advantage of +available disk space for long-term metrics storage. This feature of the database engine allows you to store a much +larger dataset than your system's available RAM. + +The database engine is currently the default method of storing metrics, but if you're not sure which database you're +using, check out your `netdata.conf` file and look for the `memory mode` setting: + +```conf +[global] + memory mode = dbengine +``` + +If `memory mode` is set to anything but `dbengine`, change it and restart Netdata using the standard command for +restarting services on your system. You're now using the database engine! + +What makes the database engine efficient? While it's structured like a traditional database, the database engine splits +data between RAM and disk. The database engine caches and indexes data on RAM to keep memory usage low, and then +compresses older metrics onto disk for long-term storage. + +When the Netdata dashboard queries for historical metrics, the database engine will use its cache, stored in RAM, to +return relevant metrics for visualization in charts. + +Now, given that the database engine uses _both_ RAM and disk, there are two other settings to consider: `page cache +size` and `dbengine multihost disk space`. + +```conf +[global] + page cache size = 32 + dbengine multihost disk space = 256 +``` + +`page cache size` sets the maximum amount of RAM (in MiB) the database engine will use for caching and indexing. +`dbengine multihost disk space` sets the maximum disk space (again, in MiB) the database engine will use for storing +compressed metrics. The default settings retain about two day's worth of metrics on a system collecting 2,000 metrics +every second. + +[**See our database engine +calculator**](/docs/store/change-metrics-storage.md#calculate-the-system-resources-RAM-disk-space-needed-to-store-metrics) +to help you correctly set `dbengine multihost disk space` based on your needs. The calculator gives an accurate estimate +based on how many child nodes you have, how many metrics your Agent collects, and more. + +With the database engine active, you can back up your `/var/cache/netdata/dbengine/` folder to another location for +redundancy. + +Now that you know how to switch to the database engine, let's cover the default round-robin database for those who +aren't ready to make the move. + +## Using the round-robin database + +In previous versions, Netdata used a round-robin database to store 1 hour of per-second metrics. + +To see if you're still using this database, or if you would like to switch to it, open your `netdata.conf` file and see +if `memory mode` option is set to `save`. + +```conf +[global] + memory mode = save +``` + +If `memory mode` is set to `save`, then you're using the round-robin database. If so, the `history` option is set to +`3600`, which is the equivalent to 3,600 seconds, or one hour. + +To increase your historical metrics, you can increase `history` to the number of seconds you'd like to store: + +```conf +[global] + # 2 hours = 2 * 60 * 60 = 7200 seconds + history = 7200 + # 4 hours = 4 * 60 * 60 = 14440 seconds + history = 14440 + # 24 hours = 24 * 60 * 60 = 86400 seconds + history = 86400 +``` + +And so on. + +Next, check to see how many metrics Netdata collects on your system, and how much RAM that uses. Visit the Netdata +dashboard and look at the bottom-right corner of the interface. You'll find a sentence similar to the following: + +> Every second, Netdata collects 1,938 metrics, presents them in 299 charts and monitors them with 81 alarms. Netdata is +> using 25 MB of memory on **netdata-linux** for 1 hour, 6 minutes and 36 seconds of real-time history. + +On this desktop system, using a Ryzen 5 1600 and 16GB of RAM, the round-robin databases uses 25 MB of RAM to store just +over an hour's worth of data for nearly 2,000 metrics. + +To increase the `history` option, you need to edit your `netdata.conf` file and increase the `history` setting. In most +installations, you'll find it at `/etc/netdata/netdata.conf`, but some operating systems place it at +`/opt/netdata/etc/netdata/netdata.conf`. + +Use `/etc/netdata/edit-config netdata.conf`, or your favorite text editor, to replace `3600` with the number of seconds +you'd like to store. + +You should base this number on two things: How much history you need for your use case, and how much RAM you're willing +to dedicate to Netdata. + +> Take care when you change the `history` option on production systems. Netdata is configured to stop its process if +> your system starts running out of RAM, but you can never be too careful. Out of memory situations are very bad. + +How much RAM will a longer history use? Let's use a little math. + +The round-robin database needs 4 bytes for every value Netdata collects. If Netdata collects metrics every second, +that's 4 bytes, per second, per metric. + +```text +4 bytes * X seconds * Y metrics = RAM usage in bytes +``` + +Let's assume your system collects 1,000 metrics per second. + +```text +4 bytes * 3600 seconds * 1,000 metrics = 14400000 bytes = 14.4 MB RAM +``` + +With that formula, you can calculate the RAM usage for much larger history settings. + +```conf +# 2 hours at 1,000 metrics per second +4 bytes * 7200 seconds * 1,000 metrics = 28800000 bytes = 28.8 MB RAM +# 2 hours at 2,000 metrics per second +4 bytes * 7200 seconds * 2,000 metrics = 57600000 bytes = 57.6 MB RAM +# 4 hours at 2,000 metrics per second +4 bytes * 14440 seconds * 2,000 metrics = 115520000 bytes = 115.52 MB RAM +# 24 hours at 1,000 metrics per second +4 bytes * 86400 seconds * 1,000 metrics = 345600000 bytes = 345.6 MB RAM +``` + +## What's next? + +Now that you have either configured database engine or round-robin database engine to store more metrics, you'll +probably want to see it in action! + +For more information about how to pan charts to view historical metrics, see our documentation on [using +charts](/web/README.md#using-charts). + +And if you'd now like to reduce Netdata's resource usage, view our [performance +guide](/docs/guides/configure/performance.md) for our best practices on optimization. + +[](<>) |