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Yesterday I rebooted the web server machine, but I'm trying to figure out why the graph below shows prior rebooting the memory almost full of cache and just a bit of active memory used. Would there be any problem keeping it the same was it was or rebooting every ~30 days is what I'm suppose to do?


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up vote 6 down vote accepted

Check out this blog post, it might shed some light on the issue.

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nice answer! short, to the point, and exactly what the OP needed. – faultyserver Nov 10 '09 at 17:36

Linux likes to use all otherwise-unused memory for disk cache. There's no performance downside, and there just might be a benefit because the disk won't need to be touched for some disk reads.

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Exactly. Using memory for cache is GOOD. Enjoy it. And whatever you do, don't reboot a Unix server every 30 days. They're meant to run for a LONG time. – Lee B Nov 10 '09 at 19:46
I think Lee B means "don't reboot a Unix server unless you have a good reason." Security updates which involve kernel updates, are a Good Reason. If someone shows you an uptime of more than 90 days, odds are very good you can show them a machine that has unpatched kernel vulnerabilities. – David Mackintosh Nov 10 '09 at 21:04

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