Many people use NFS to keep the sites/default/files directory outside of the normal webroot of a Drupal install.
However, I'm running the entire Drupal install over NFS.
When the site has not been accessed in some time, there's a solid 15-20 seconds of delay before a page loads. After that everything is fine. I have Drupal's page caching turned off for these tests to provide consistent results.
Initially I found that PHP's
realpath_cache needed to be adjusted, because the default of 16k is not enough to handle all of paths Drupal loads when bootstrapping. I have this raised to 128k, and I see now that the utilized cache size goes up to around 40-50kb (after browsing around the site all over to "trigger" more file loads).
However, that does not seem to affect performance at all. Those cache entries expire anyway and will eventually PHP will need to hit the FS again.
I also have the built in "poor mans cron" disabled, so it's not related to Drupal running a bunch of cron tasks on that page load.
I suspect it may be related to NFS.
Is anyone else running a Drupal install completely over NFS, or have you in the past and come to any conclusions that may help?