I have an error showing up in the logs for a site:
"[Sun Jan 13 13:27:11 2013] [error] [client IP] mv: cannot move
/path/public_html/system/expressionengine/cache/page_cache' to/path/public_html/system/expressionengine/cache/page_cache_delete': No such file or directory
[Sun Jan 13 13:26:48 2013] [error] [client IP] cannot move
'IP' and 'path' represent a real ip and system path.
This site doesn't make use of page caching, but I understand EE can still try to manage it's cache. Normally I wouldn't be concerned, but this particular site has periodic spikes where server load will jump from an average of .5 to 1.5 up to 80 to 100. This crashes the server, and one happened this afternoon.
My host is running loadwatch on the site, and it shows a large number of apache processes without a correspondingly large number of user connections. They also said that there was an overload on the servers memory, which was followed by the load / process spike.
Why do I think these might be related? http://ellislab.com/forums/viewthread/152522/#753282 This forum thread from several years ago on an EE 1 site. It's the only lead I have right now on why this site could be running perfectly fine 99% of the time and then periodically blowing up and taking down a VPS that's more than capable of running it.
Has anyone seen something like this happen on their own sites? If not, any suggestions for how to monitor what's causing spikes like this? My host doesn't seem to have any more to offer as far as tracking, so I can't trace it down to specifically what's causing the spike right now. Any help is appreciated.