docs: clarify -retentionPeriod flag usage (#4417)

app/vmstorage: clarify the min value for `-retentionPeriod` flag

Co-authored-by: Roman Khavronenko <roman@victoriametrics.com>

README.md

@@ -147,7 +147,7 @@ VictoriaMetrics can also be installed via these installation methods:
 The following command-line flags are used the most:
 
 * `-storageDataPath` - VictoriaMetrics stores all the data in this directory. Default path is `victoria-metrics-data` in the current working directory.
-* `-retentionPeriod` - retention for stored data. Older data is automatically deleted. Default retention is 1 month. See [the Retention section](#retention) for more details.
+* `-retentionPeriod` - retention for stored data. Older data is automatically deleted. Default retention is 1 month. The minimum retention period is 24h or 1d. See [the Retention section](#retention) for more details. The minimum retention period is 24h or 1d.
 
 Other flags have good enough default values, so set them only if you really need this. Pass `-help` to see [all the available flags with description and default values](#list-of-command-line-flags).
 
@@ -1569,7 +1569,7 @@ See also [how to work with snapshots](#how-to-work-with-snapshots).
 
 ## Retention
 
-Retention is configured with the `-retentionPeriod` command-line flag, which takes a number followed by a time unit character - `h(ours)`, `d(ays)`, `w(eeks)`, `y(ears)`. If the time unit is not specified, a month is assumed. For instance, `-retentionPeriod=3` means that the data will be stored for 3 months and then deleted. The default retention period is one month.
+Retention is configured with the `-retentionPeriod` command-line flag, which takes a number followed by a time unit character - `h(ours)`, `d(ays)`, `w(eeks)`, `y(ears)`. If the time unit is not specified, a month is assumed. For instance, `-retentionPeriod=3` means that the data will be stored for 3 months and then deleted. The default retention period is one month. The minimum retention period is 24h or 1d.
 
 Data is split in per-month partitions inside `<-storageDataPath>/data/{small,big}` folders.
 Data partitions outside the configured retention are deleted on the first day of the new month.
@@ -2474,7 +2474,7 @@ Pass `-help` to VictoriaMetrics in order to see the list of supported command-li
      Supports an array of values separated by comma or specified via multiple flags.
   -retentionPeriod value
      Data with timestamps outside the retentionPeriod is automatically deleted. See also -retentionFilter
-     The following optional suffixes are supported: h (hour), d (day), w (week), y (year). If suffix isn't set, then the duration is counted in months (default 1)
+     The following optional suffixes are supported: h (hour), d (day), w (week), y (year). If suffix isn't set, then the duration is counted in months (default 1). The minimum retention period is 24h or 1d.
   -retentionTimezoneOffset duration
      The offset for performing indexdb rotation. If set to 0, then the indexdb rotation is performed at 4am UTC time per each -retentionPeriod. If set to 2h, then the indexdb rotation is performed at 4am EET time (the timezone with +2h offset)
   -search.cacheTimestampOffset duration

app/vmstorage/main.go

@@ -23,7 +23,7 @@ import (
 )
 
 var (
-	retentionPeriod       = flagutil.NewDuration("retentionPeriod", "1", "Data with timestamps outside the retentionPeriod is automatically deleted. See also -retentionFilter")
+	retentionPeriod       = flagutil.NewDuration("retentionPeriod", "1", "Data with timestamps outside the retentionPeriod is automatically deleted. The minimum retentionPeriod is 24h or 1d. See also -retentionFilter")
 	snapshotAuthKey       = flag.String("snapshotAuthKey", "", "authKey, which must be passed in query string to /snapshot* pages")
 	forceMergeAuthKey     = flag.String("forceMergeAuthKey", "", "authKey, which must be passed in query string to /internal/force_merge pages")
 	forceFlushAuthKey     = flag.String("forceFlushAuthKey", "", "authKey, which must be passed in query string to /internal/force_flush pages")

docs/Cluster-VictoriaMetrics.md

@@ -1364,7 +1364,7 @@ Below is the output for `/path/to/vmstorage -help`:
      Supports an array of values separated by comma or specified via multiple flags.
   -retentionPeriod value
      Data with timestamps outside the retentionPeriod is automatically deleted. See also -retentionFilter
-     The following optional suffixes are supported: h (hour), d (day), w (week), y (year). If suffix isn't set, then the duration is counted in months (default 1)
+     The following optional suffixes are supported: h (hour), d (day), w (week), y (year). If suffix isn't set, then the duration is counted in months (default 1). The minimum retentionPeriod is 24h or 1d.
   -retentionTimezoneOffset duration
      The offset for performing indexdb rotation. If set to 0, then the indexdb rotation is performed at 4am UTC time per each -retentionPeriod. If set to 2h, then the indexdb rotation is performed at 4am EET time (the timezone with +2h offset)
   -rpc.disableCompression

docs/README.md

@@ -150,7 +150,7 @@ VictoriaMetrics can also be installed via these installation methods:
 The following command-line flags are used the most:
 
 * `-storageDataPath` - VictoriaMetrics stores all the data in this directory. Default path is `victoria-metrics-data` in the current working directory.
-* `-retentionPeriod` - retention for stored data. Older data is automatically deleted. Default retention is 1 month. See [the Retention section](#retention) for more details.
+* `-retentionPeriod` - retention for stored data. Older data is automatically deleted. Default retention is 1 month. The minimum retention period is 24h or 1d. See [the Retention section](#retention) for more details.
 
 Other flags have good enough default values, so set them only if you really need this. Pass `-help` to see [all the available flags with description and default values](#list-of-command-line-flags).
 
@@ -1572,7 +1572,7 @@ See also [how to work with snapshots](#how-to-work-with-snapshots).
 
 ## Retention
 
-Retention is configured with the `-retentionPeriod` command-line flag, which takes a number followed by a time unit character - `h(ours)`, `d(ays)`, `w(eeks)`, `y(ears)`. If the time unit is not specified, a month is assumed. For instance, `-retentionPeriod=3` means that the data will be stored for 3 months and then deleted. The default retention period is one month.
+Retention is configured with the `-retentionPeriod` command-line flag, which takes a number followed by a time unit character - `h(ours)`, `d(ays)`, `w(eeks)`, `y(ears)`. If the time unit is not specified, a month is assumed. For instance, `-retentionPeriod=3` means that the data will be stored for 3 months and then deleted. The default retention period is one month. The minimum retention period is 24h or 1d.
 
 Data is split in per-month partitions inside `<-storageDataPath>/data/{small,big}` folders.
 Data partitions outside the configured retention are deleted on the first day of the new month.
@@ -2477,7 +2477,7 @@ Pass `-help` to VictoriaMetrics in order to see the list of supported command-li
      Supports an array of values separated by comma or specified via multiple flags.
   -retentionPeriod value
      Data with timestamps outside the retentionPeriod is automatically deleted. See also -retentionFilter
-     The following optional suffixes are supported: h (hour), d (day), w (week), y (year). If suffix isn't set, then the duration is counted in months (default 1)
+     The following optional suffixes are supported: h (hour), d (day), w (week), y (year). If suffix isn't set, then the duration is counted in months (default 1). The minimum retentionPeriod is 24h or 1d.
   -retentionTimezoneOffset duration
      The offset for performing indexdb rotation. If set to 0, then the indexdb rotation is performed at 4am UTC time per each -retentionPeriod. If set to 2h, then the indexdb rotation is performed at 4am EET time (the timezone with +2h offset)
   -search.cacheTimestampOffset duration

docs/Single-server-VictoriaMetrics.md

@@ -158,7 +158,7 @@ VictoriaMetrics can also be installed via these installation methods:
 The following command-line flags are used the most:
 
 * `-storageDataPath` - VictoriaMetrics stores all the data in this directory. Default path is `victoria-metrics-data` in the current working directory.
-* `-retentionPeriod` - retention for stored data. Older data is automatically deleted. Default retention is 1 month. See [the Retention section](#retention) for more details.
+* `-retentionPeriod` - retention for stored data. Older data is automatically deleted. Default retention is 1 month. The minimum retention period is 24h or 1d. See [the Retention section](#retention) for more details.
 
 Other flags have good enough default values, so set them only if you really need this. Pass `-help` to see [all the available flags with description and default values](#list-of-command-line-flags).
 
@@ -1580,7 +1580,7 @@ See also [how to work with snapshots](#how-to-work-with-snapshots).
 
 ## Retention
 
-Retention is configured with the `-retentionPeriod` command-line flag, which takes a number followed by a time unit character - `h(ours)`, `d(ays)`, `w(eeks)`, `y(ears)`. If the time unit is not specified, a month is assumed. For instance, `-retentionPeriod=3` means that the data will be stored for 3 months and then deleted. The default retention period is one month.
+Retention is configured with the `-retentionPeriod` command-line flag, which takes a number followed by a time unit character - `h(ours)`, `d(ays)`, `w(eeks)`, `y(ears)`. If the time unit is not specified, a month is assumed. For instance, `-retentionPeriod=3` means that the data will be stored for 3 months and then deleted. The default retention period is one month. The minimum retention period is 24h or 1d.
 
 Data is split in per-month partitions inside `<-storageDataPath>/data/{small,big}` folders.
 Data partitions outside the configured retention are deleted on the first day of the new month.