Update change-metrics-storage.md (#14640)
Chris Akritidis committed
Mar 1, 2023 at 06:52 UTC
b352d2be8354f2fda8538feab2bfcfb191eae593
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docs/store/change-metrics-storage.md
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@@ -38,11 +38,22 @@ on the maximum retention and the memory used by Netdata is described in detail,
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# Tier 1, per minute data
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dbengine tier 1 multihost disk space MB = 128
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-
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+ dbengine tier 1 update every iterations = 60
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+
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# Tier 2, per hour data
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dbengine tier 2 multihost disk space MB = 64
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+ dbengine tier 2 update every iterations = 60
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```
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+The default "update every iterations" of 60 means that if a metric is collected per second in Tier 0, then
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+we will have a data point every minute in tier 1 and every minute in tier 2.
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+
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+You may add, or remove tiers and/or modify these multipliers, as long as the product of all the "update every" does not exceed 65535.
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+e.g. If you simply add a fourth tier by setting `storage tiers` to 4 and defining the disk space for it,
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+the product of the update every will be 60 * 60 * 60 = 216,000, which is > 65535. So you'd need to reduce
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+the `update every iterations` of the tiers, to stay under the limit.
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+
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The exact retention that can be achieved by each tier depends on the number of metrics collected. The more
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the metrics, the smaller the retention that will fit in a given size. The general rule is that Netdata needs
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about **1 byte per data point on disk for tier 0**, and **4 bytes per data point on disk for tier 1 and above**.