openstack/swift
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Adds useful dispersion info from changelog

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Change-Id: I1a45088fc32620b02ff9a754b02ec1eb75a59d6e
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Brian Cline 2015-09-01 10:51:20 -05:00
parent cde92d98dc
commit 615c7a204b
1 changed files with 15 additions and 0 deletions
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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".
*********************
Partition Shift Value
*********************