openstack/swift
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Merge "Adds useful dispersion info from changelog"

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Jenkins 2015-09-02 23:14:11 +00:00 committed by Gerrit Code Review
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doc/source/overview_ring.rst
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@ -168,6 +168,21 @@ on them than the disks in nodes A and B. If 80% full is the warning
threshold for the cluster, node C's disks will reach 80% full while A
and B's disks are only 72.7% full.
**********
Dispersion
**********
With each rebalance, the ring builder calculates a dispersion metric. This is
the percentage of partitions in the ring that have too many replicas within a
particular failure domain.
For example, if you have three servers in a cluster but two replicas for a
partition get placed onto the same server, that partition will count towards the
dispersion metric.
A lower dispersion value is better, and the value can be used to find the proper
value for "overload".
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Partition Shift Value
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