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docs/Single-server-VictoriaMetrics.md: explain why free disk space shortage may negatively impact VictoriaMetrics performance

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docs/README.md
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@ -1226,9 +1226,18 @@ values and timestamps. These are sorted and compressed raw time series values. A
index files for searching for specific series in the values and timestamps files.
`Parts` are periodically merged into the bigger parts. The resulting `part` is constructed
under `<-storageDataPath>/data/{small,big}/YYYY_MM/tmp` subdirectory. When the resulting `part` is complete, it is atomically moved from the `tmp`
under `<-storageDataPath>/data/{small,big}/YYYY_MM/tmp` subdirectory.
When the resulting `part` is complete, it is atomically moved from the `tmp`
to its own subdirectory, while the source parts are atomically removed. The end result is that the source
parts are substituted by a single resulting bigger `part` in the `<-storageDataPath>/data/{small,big}/YYYY_MM/` directory.
VictoriaMetrics doesn't merge parts if their summary size exceeds free disk space.
This prevents from potential out of disk space errors during merge.
The number of parts may significantly increase over time under free disk space shortage.
This increases overhead during data querying, since VictoriaMetrics needs to read data from
bigger number of parts per each request. That's why it is recommended to have at least 20%
of free disk space under directory pointed by `-storageDataPath` command-line flag.
Information about merging process is available in [single-node VictoriaMetrics](https://grafana.com/dashboards/10229)
and [clustered VictoriaMetrics](https://grafana.com/grafana/dashboards/11176) Grafana dashboards.
See more details in [monitoring docs](#monitoring).

11
docs/Single-server-VictoriaMetrics.md
View file

@ -1230,9 +1230,18 @@ values and timestamps. These are sorted and compressed raw time series values. A
index files for searching for specific series in the values and timestamps files.
`Parts` are periodically merged into the bigger parts. The resulting `part` is constructed
under `<-storageDataPath>/data/{small,big}/YYYY_MM/tmp` subdirectory. When the resulting `part` is complete, it is atomically moved from the `tmp`
under `<-storageDataPath>/data/{small,big}/YYYY_MM/tmp` subdirectory.
When the resulting `part` is complete, it is atomically moved from the `tmp`
to its own subdirectory, while the source parts are atomically removed. The end result is that the source
parts are substituted by a single resulting bigger `part` in the `<-storageDataPath>/data/{small,big}/YYYY_MM/` directory.
VictoriaMetrics doesn't merge parts if their summary size exceeds free disk space.
This prevents from potential out of disk space errors during merge.
The number of parts may significantly increase over time under free disk space shortage.
This increases overhead during data querying, since VictoriaMetrics needs to read data from
bigger number of parts per each request. That's why it is recommended to have at least 20%
of free disk space under directory pointed by `-storageDataPath` command-line flag.
Information about merging process is available in [single-node VictoriaMetrics](https://grafana.com/dashboards/10229)
and [clustered VictoriaMetrics](https://grafana.com/grafana/dashboards/11176) Grafana dashboards.
See more details in [monitoring docs](#monitoring).