openstack/swift
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Merge "Add dispersion --verbose example to admin guide"

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Jenkins 2016-05-25 18:57:20 +00:00 committed by Gerrit Code Review
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doc/source/admin_guide.rst
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@ -115,6 +115,40 @@ This will not only display the percentage but will also display a dispersion
table that lists partition dispersion by tier. You can use this table to figure
out were you need to add capacity or to help tune an :ref:`ring_overload` value.
Now let's take an example with 1 region, 3 zones and 4 devices. Each device has
the same weight, and the ``dispersion --verbose`` might show the following::
Dispersion is 50.000000, Balance is 0.000000, Overload is 0.00%
Required overload is 33.333333%
Worst tier is 50.000000 (r1z3)
--------------------------------------------------------------------------
Tier Parts % Max 0 1 2 3
--------------------------------------------------------------------------
r1 256 0.00 3 0 0 0 256
r1z1 192 0.00 1 64 192 0 0
r1z1-127.0.0.1 192 0.00 1 64 192 0 0
r1z1-127.0.0.1/sda 192 0.00 1 64 192 0 0
r1z2 192 0.00 1 64 192 0 0
r1z2-127.0.0.2 192 0.00 1 64 192 0 0
r1z2-127.0.0.2/sda 192 0.00 1 64 192 0 0
r1z3 256 50.00 1 0 128 128 0
r1z3-127.0.0.3 256 50.00 1 0 128 128 0
r1z3-127.0.0.3/sda 192 0.00 1 64 192 0 0
r1z3-127.0.0.3/sdb 192 0.00 1 64 192 0 0
The first line reports that there are 256 partitions with 3 copies in region 1;
and this is an expected output in this case (single region with 3 replicas) as
reported by the "Max" value.
However, there is some inbalance in the cluster, more precisely in zone 3. The
"Max" reports a maximum of 1 copy in this zone; however 50.00% of the partitions
are storing 2 replicas in this zone (which is somewhat expected, because there
are more disks in this zone).
You can now either add more capacity to the other zones, decrease the total
weight in zone 3 or set the overload value to 33.333333%.
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Scripting Ring Creation
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