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From: Mike Jakubik <mikej@rogers.com>
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Subject: Changing balance algorithm on existing gmirror
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Hello,

I was wondering if it was possible to change the balance algorithm on an
existing gmirror setup, without destroying any data/configuration. I am
trying to do some benchmarks, to compare which would work best for my
needs. Speaking of.. I noticed this strange behavior, while running a
concurrent csup session and extracting the ports tar file, where one
disk would get 100% usage, but second around 10.

Disks   ad4   ad6
KB/t   2.12  2.30
tps     322   394
MB/s   0.67  0.89
% busy   98     8

I am using the round-robin algorithm here, in case it matters.