Following extensive researching, testing and talking to Dreamhost’s Support team it transpires that their set-up of XCache conflicts with W3 Total Cache (W3TC) for WordPress.
I can also confirm from an IM conversation with a member of their support team that although Memcached is installed and enabled on their VPS environments, they do NOT run it. This is reserved only for Dedicated hosting packages.
TEST PROCESS
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[]Performance testing was measured using a combination of Network performance via Chrome’s inspect element and Apache Benchmark.
[]Performance testing was measured using a combination of Network performance via Chrome’s inspect element and Apache Benchmark.
[]Chrome Incognito was used, making sure to reload the browser window using Ctrl + F5 to do a full browser cache clear.
[]phpinfo.php was used to make sure Opcahe was enabled. The VPS environemnt was also restarted after Opcache was enabled.
[]Each test was be performed 3 times, with only the average figure being used in the summary results graph. This is to allow for the usual variation that comes from testing web technologies.
[]As I go through each step of the test, I am adding each enhancement so the end is the cumulative effects of all the changes.
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DETAILED RESULTS DATA
For the detailed data results see Google spreadsheet https://docs.google.com/spreadsheets/d/1MqtRClOBlnyCIR1bE1qY-SAPeGIu2xP1r_eUeVU1UxM/ or snapshot image.
OPTIMUM SETTING
The optimum settings that I discovered through this lengthy process of communications with Dreamhost, supplemented by detailed testing of W3TC setting variations with Network performance via Chrome’s inspect element and Apache Benchmark is:
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[*] For fully optimal settings from the test please see Dreamhost VPS WordPress Performance Optimisation Report
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