VictoriaMetrics/docs/FAQ.md

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FAQ

What is the main purpose of VictoriaMetrics?

To provide the best monitoring solution.

Who uses VictoriaMetrics?

See case studies.

Which features does VictoriaMetrics have?

See these docs.

Are there performance comparisons with other solutions?

Yes. See these benchmarks.

How to start using VictoriaMetrics?

See these docs.

Does VictoriaMetrics support replication?

Yes. See these docs for details.

Can I use VictoriaMetrics instead of Prometheus?

Yes in most cases. VictoriaMetrics can substitute Prometheus in the following aspects:

• Prometheus-compatible service discovery and target scraping can be done with vmagent and with single-node VictoriaMetrics - see these docs.
• Prometheus-compatible alerting rules and recording rules can be processed with vmalert.
• Prometheus-compatible querying in Grafana is supported by VictoriaMetrics. See these docs.

What is the difference between vmagent and Prometheus?

While both vmagent and Prometheus may scrape Prometheus targets (aka /metrics pages) according to the provided Prometheus-compatible scrape configs and send data to multiple remote storage systems, vmagent has the following additional features:

• vmagent usually requires lower amounts of CPU, RAM and disk IO comparing to Prometheus when scraping big number of targets (more than 1000) or targets with big number of exposed metrics.
• vmagent provides independent disk-backed buffers per each configured remote storage (aka -remoteWrite.url). This means that slow or temporarily unavailable storage doesn't prevent from sending data to healthy storage in parallel. Prometheus uses a single shared buffer for all the configured remote storage systems (aka remote_write->url) with the hardcoded retention of 2 hours.
• vmagent may accept, relabel and filter data obtained via multiple data ingestion protocols additionally to data scraped from Prometheus targets. I.e. it supports both pull and push protocols for data ingestion. See these docs for details.
• vmagent may be used in different use cases:
  • IoT and edge monitoring
  • Drop-in replacement for Prometheus
  • Replication and High Availability
  • Relabeling and Filtering
  • Splitting data streams among multiple systems
  • Prometheus remote_write proxy

What is the difference between vmagent and Prometheus agent?

Both vmagent and Prometheus agent serve the same purpose - to efficently scrape Prometheus-compatible targets at the edge. The have the following differences:

• vmagent usually requires lower amounts of CPU, RAM and disk IO comparing to Prometheus agent.
• Prometheus agent supports only pull-based data collection (e.g. it can scrape Prometheus-compatible targets), while vmagent supports both pull and push data collection - it can accept data via many popular data ingestion protocols such as InfluxDB line protocol, Graphite protocol, OpenTSDB protocol, DataDog protocol, Prometheus protocol, CSV and JSON - see these docs.
• vmagent can easily scale horizontally to multiple instances for scraping big number of targets - see these docs.
• vmagent supports improved relabeling.
• vmagent can limit the number of scraped metrics per target. See these docs.
• vmagent supports loading scrape configs from multiple files - see these docs.
• vmagent supports data reading and data writing from/to Kafka - see these docs.
• vmagent can read and update scrape configs from http and https urls, while Prometheus agent can read scrape configs only from local filesystem.

Is it safe to enable remote write in Prometheus?

Yes. Prometheus continues writing data to local storage after enabling remote write, so all the existing local storage data and new data is available for querying via Prometheus as usual.

It is recommended using vmagent for scraping Prometheus targets and writing data to VictoriaMetrics.

How does VictoriaMetrics compare to other remote storage solutions for Prometheus such as M3 from Uber, Thanos, Cortex, etc.?

VictoriaMetrics is simpler, faster, more cost-effective and it provides MetricsQL query language based on PromQL. The simplicity is twofold:

• It is simpler to configure and operate. There is no need in configuring sidecars, fighting gossip protocol or setting up third-party systems such as Consul, Cassandra, DynamoDB or Memcached.
• VictoriaMetrics has simpler architecture. This means less bugs and more useful features in the long run comparing to competing TSDBs.

See comparing Thanos to VictoriaMetrics cluster and Remote Write Storage Wars talk from PromCon 2019.

VictoriaMetrics also uses less RAM than Thanos components.

What is the difference between VictoriaMetrics and QuestDB?

• QuestDB needs more than 20x storage space than VictoriaMetrics. This translates to higher storage costs and slower queries over historical data, which must be read from the disk.
• QuestDB is much harder to setup and operate than VictoriaMetrics. Compare setup instructions for QuestDB to setup instructions for VictoriaMetrics.
• VictoriaMetrics provides MetricsQL query language, which is better suited for typical queries over time series data than SQL-like query language provided by QuestDB. See this article for details.
• VictoriaMetrics can be queried via Prometheus querying API and via Graphite API.
• Thanks to PromQL support, VictoriaMetrics can be used as a drop-in replacement for Prometheus in Grafana, while QuestDB needs full rewrite of existing dashboards in Grafana.
• Thanks to Prometheus remote_write API support, VictoriaMetrics can be used as a long-term storage for Prometheus or for vmagent, while QuestDB has no integration with Prometheus.
• QuestDB supports smaller range of popular data ingestion protocols compared to VictoriaMetrics (compare to the list of supported data ingestion protocols for VictoriaMetrics).
• VictoriaMetrics supports backfilling (e.g. storing historical data) out of the box, while QuestDB provides very limited support for backfilling.

What is the difference between VictoriaMetrics and Cortex?

VictoriaMetrics is similar to Cortex in the following aspects:

• Both systems accept data from vmagent or Prometheus via standard remote_write API, i.e. there is no need in running sidecars unlike in Thanos case.
• Both systems support multi-tenancy out of the box. See the corresponding docs for VictoriaMetrics.
• Both systems support data replication. See replication in Cortex and replication in VictoriaMetrics.
• Both systems scale horizontally to multiple nodes. See these docs for details.
• Both systems support alerting and recording rules via the corresponding tools such as vmalert.
• Both systems can be queried via Prometheus querying API and integrate perfectly with Grafana.

The main differences between Cortex and VictoriaMetrics:

• Cortex re-uses Prometheus source code, while VictoriaMetrics is written from scratch.
• Cortex heavily relies on third-party services such as Consul, Memcache, DynamoDB, BigTable, Cassandra, etc. This may increase operational complexity and reduce system reliability comparing to VictoriaMetrics' case, which doesn't use any external services. Compare Cortex Architecture to VictoriaMetrics architecture.
• VictoriaMetrics provides production-ready single-node solution, which is much easier to setup and operate than Cortex cluster.
• Cortex may lose up to 12 hours of recent data on Ingestor failure - see the corresponding docs. VictoriaMetrics may lose only a few seconds of recent data, which isn't synced to persistent storage yet. See this article for details.
• Cortex is usually slower and requires more CPU and RAM than VictoriaMetrics. See this talk from adidas at PromCon 2019 and other case studies.
• VictoriaMetrics accepts data in multiple popular data ingestion protocols additionally to Prometheus remote_write protocol - InfluxDB, OpenTSDB, Graphite, CSV, JSON, native binary. See these docs for details.
• VictoriaMetrics provides MetricsQL query language, while Cortex provides PromQL query language.
• VictoriaMetrics can be queried via Graphite API.

What is the difference between VictoriaMetrics and Thanos?

• Thanos re-uses Prometheus source code, while VictoriaMetrics is written from scratch.
• VictoriaMetrics accepts data via standard remote_write API for Prometheus, while Thanos uses non-standard Sidecar, which must run alongside each Prometheus instance.
• Thanos Sidecar requires disabling data compaction in Prometheus, which may hurt Prometheus performance and increase RAM usage. See these docs for more details.
• Thanos stores data in object storage (Amazon S3 or Google GCS), while VictoriaMetrics stores data in block storage (GCP persistent disks, Amazon EBS or bare metal HDD). While object storage is usually less expensive, block storage provides much lower latencies and higher throughput. VictoriaMetrics works perfectly with HDD-based block storage - there is no need in using more expensive SSD or NVMe disks in most cases.
• Thanos may lose up to 2 hours of recent data, which wasn't uploaded yet to object storage. VictoriaMetrics may lose only a few seconds of recent data, which isn't synced to persistent storage yet. See this article for details.
• VictoriaMetrics provides production-ready single-node solution, which is much easier to setup and operate than Thanos components.
• Thanos may be harder to setup and operate comparing to VictoriaMetrics, since it has more moving parts, which can be connected with less reliable networks. See this article for details.
• Thanos is usually slower and requires more CPU and RAM than VictoriaMetrics. See this talk from adidas at PromCon 2019.
• VictoriaMetrics accepts data in multiple popular data ingestion protocols additionally to Prometheus remote_write protocol - InfluxDB, OpenTSDB, Graphite, CSV, JSON, native binary. See these docs for details.
• VictoriaMetrics provides MetricsQL query language, while Thanos provides PromQL query language.
• VictoriaMetrics can be queried via Graphite API.

How does VictoriaMetrics compare to InfluxDB?

• VictoriaMetrics requires 10x less RAM and it works faster.
• VictoriaMetrics needs lower amounts of storage space than InfluxDB on production data.
• VictoriaMetrics provides better query language - MetricsQL - than InfluxQL or Flux. See this tutorial for details.
• VictoriaMetrics accepts data in multiple popular data ingestion protocols additionally to InfluxDB - Prometheus remote_write, OpenTSDB, Graphite, CSV, JSON, native binary. See these docs for details.
• VictoriaMetrics can be queried via Graphite API.

How does VictoriaMetrics compare to TimescaleDB?

• TimescaleDB insists on using SQL as a query language. While SQL is more powerful than PromQL, this power is rarely required during typical TSDB usage. Real-world queries usually look clearer and simpler when written in PromQL than in SQL.
• VictoriaMetrics requires up to 70x less storage space comparing to TimescaleDB for storing the same amount of time series data. The gap in storage space usage can be lowered from 70x to 3x if compression in TimescaleDB is properly configured (it isn't an easy task in general case :)).
• VictoriaMetrics requires up to 10x less CPU and RAM resources than TimescaleDB for processing production data. See this article for details.
• TimescaleDB is harder to setup, configure and operate than VictoriaMetrics (see how to run VictoriaMetrics).
• VictoriaMetrics accepts data in multiple popular data ingestion protocols - InfluxDB, OpenTSDB, Graphite, CSV, while TimescaleDB supports only SQL inserts.
• VictoriaMetrics can be queried via Graphite API.

Does VictoriaMetrics use Prometheus technologies like other clustered TSDBs built on top of Prometheus such as Thanos or Cortex?

No. VictoriaMetrics core is written in Go from scratch by fasthttp author. The architecture is optimized for storing and querying large amounts of time series data with high cardinality. VictoriaMetrics storage uses certain ideas from ClickHouse. Special thanks to Alexey Milovidov.

What is the pricing for VictoriaMetrics?

The following versions are open source and free:

• Single-node version.
• Cluster version.

We provide commercial support for both versions. Contact us for the pricing.

The following commercial versions of VictoriaMetrics are available:

• Managed VictoriaMetrics at AWS (aka managed Prometheus).

The following commercial versions of VictoriaMetrics are planned:

• Managed VictoriaMetrics at Google Cloud.
• Cloud monitoring solution based on VictoriaMetrics.

Contact us for more information on our plans.

Why VictoriaMetrics doesn't support Prometheus remote read API?

Remote read API requires transferring all the raw data for all the requested metrics over the given time range. For instance, if a query covers 1000 metrics with 10K values each, then the remote read API had to return 1000*10K=10M metric values to Prometheus. This is slow and expensive. Prometheus remote read API isn't intended for querying foreign data aka global query view. See this issue for details.

So just query VictoriaMetrics directly via vmui, Prometheus Querying API or via Prometheus datasource in Grafana.

Does VictoriaMetrics deduplicate data from Prometheus instances scraping the same targets (aka HA pairs)?

Yes. See these docs for details.

Where is the source code of VictoriaMetrics?

Source code for the following versions is available in the following places:

• Single-node version
• Cluster version

Does VictoriaMetrics fit for data from IoT sensors and industrial sensors?

VictoriaMetrics is able to handle data from hundreds of millions of IoT sensors and industrial sensors. It supports high cardinality data, perfectly scales up on a single node and scales horizontally to multiple nodes.

Where can I ask questions about VictoriaMetrics?

Questions about VictoriaMetrics can be asked via the following channels:

• Slack channel
• Telegram channel
• Google group

Where can I file bugs and feature requests regarding VictoriaMetrics?

File bugs and feature requests here.

Where I can find information about multi-tenancy?

See these docs. Multitenancy is supported only by cluster version of VictoriaMetrics.

How to set a memory limit for VictoriaMetrics components?

All the VictoriaMetrics component provide command-line flags to control the size of internal buffers and caches: -memory.allowedPercent and -memory.allowedBytes (pass -help to any VictoriaMetrics component in order to see the description for these flags). These limits don't take into account additional memory, which may be needed for processing incoming queries. Hard limits may be enforced only by the OS via cgroups, Docker (see these docs) or Kubernetes (see these docs).

Memory usage for VictoriaMetrics components can be tuned according to the following docs:

• Capacity planning for single-node VictoriaMetrics
• Capacity planning for cluster VictoriaMetrics
• Troubleshooting for vmagent
• Troubleshooting for single-node VictoriaMetrics

How can I run VictoriaMetrics on FreeBSD?

VictoriaMetrics is included in FreeBSD ports, so just install it from there. See this link.

Does VictoriaMetrics support Graphite query language?

Yes. See these docs.

What is active time series?

A time series is uniquely identified by its name plus a set of its labels. For example, temperature{city="NY",country="US"} and temperature{city="SF",country="US"} are two distinct series, since they differ by city label. A time series is considered active if it receives at least a single new sample during the last hour.

What is high churn rate?

If old time series are constantly substituted by new time series at a high rate, then such a state is called high churn rate. High churn rate has the following negative consequences:

• Increased total number of time series stored in the database.
• Increased size of inverted index, which is stored at <-storageDataPath>/indexdb, since the inverted index contains entries for every label of every time series with at least a single ingested sample
• Slow down of queries over multiple days.

The main reason for high churn rate is a metric label with frequently changed value. Examples of such labels:

• queryid, which changes with each query at postgres_exporter.
• app_name or deployment_id, which changes with each new deployment in Kubernetes.
• A label derived from the current time such as timestamp, minute or hour.
• A hash or uuid label, which changes frequently.

The solution against high churn rate is to identify and eliminate labels with frequently changed values. The /api/v1/status/tsdb page can help determining these labels.

What is high cardinality?

High cardinality usually means high number of active time series. High cardinality may lead to high memory usage and/or to high percentage of slow inserts. The source of high cardinality is usually a label with big number of unique values, which presents in big share of the ingested time series. The solution is to identify and remove the source of high cardinality with the help of /api/v1/status/tsdb.

What is slow insert?

VictoriaMetrics maintains in-memory cache for mapping of active time series into internal series ids. The cache size depends on the available memory for VictoriaMetrics in the host system. If the information about all the active time series doesn't fit the cache, then VictoriaMetrics needs to read and unpack the information from disk on every incoming sample for time series missing in the cache. This operation is much slower than the cache lookup, so such insert is named slow insert. High percentage of slow inserts on the official dashboard for VictoriaMetrics indicates on memory shortage for the current number of active time series. Such a condition usually leads to significant slowdown for data ingestion, to significantly increased disk IO and CPU usage. The solution is to add more memory or to reduce the number of active time series. The /api/v1/status/tsdb page can be helpful for locating the source of high number of active time seriess - see these docs.

How to optimize MetricsQL query?

See this article.

Why MetricsQL isn't 100% compatible with PromQL?

MetricsQL provides better user experience than PromQL. It fixes a few annoying issues in PromQL. This prevents MetricsQL to be 100% compatible with PromQL. See this article for details.

How to migrate data from Prometheus to VictoriaMetrics?

Please see these docs.

How to migrate data from InfluxDB to VictoriaMetrics?

Please see these docs.

How to migrate data from OpenTSDB to VictoriaMetrics?

Please see these docs.

How to migrate data from Graphite to VictoriaMetrics?

Please use whisper-to-graphite tool for reading the data from Graphite and pushing it to VictoriaMetrics via Graphite import API.

Why do same metrics have differences in VictoriaMetrics and Prometheus dashboards?

There could be a slight difference in stored values for time series. Due to different compression algorithms, VM may reduce precision for float values with more than 12 significant decimal digits. Please see this article

The query engine may behave differently for some functions. Please see this article