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Unexplained loads seen on a Linux webserver

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Bugger. Well then I'd suggest checking what Apache modules are loaded. There are a few which do caching (mod_cache, mod_file_cache, mod_mem_cache, mod_disk_cache). If your system is running any, disable them and see if that fixes it.

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Almost 400 megs of RAM released in the second screenshot compared to the first one.

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And an extra 80 MB has been cached (before 10 MB, after 90 MB).

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So for those following this thrilling game, have a quick look here:

 

post-544-1223372907.jpg

 

Just a quick snapshot from 5 minutes ago. I got my guys to add a 2Gb swap file this morning.

 

So then I write to them and say:

 

 

Now as you know I know NOTHING about servers - but why is it now using the SWAP FILE??? Its only using 43.9% of the regular RAM according to the stats, so should never actually need the new SWAP file?

 

Or...

 

Do we have faulty RAM? Is RAM not being used correctly by the system? Is load actually higher than we think, or it appears?

And they replied:

 

 

Jonathan,

 

This is simply how Linux VM works. Please see http://www.csn.ul.ie/~mel/projects/vm/guid.../understand.pdf for in depth details in how this is working.

 

Regards,

Erik

And that links to a 177 page PDF, so don't even go there!!!

 

But I am like...if it never needed the SWAP file...why is it now using it then???

 

Edit: JK being dumb and deleted.

 

I can get them of course to also add an extra 1GB of real RAM, but they seem to be saying still that this is still NOT the problem, and that the system is just using

the swap file "because it can".

 

Opinions?

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I mean 0.23% is 460Mb from a 2GB swap file which sounds significant to my small brain.

0.23% of 2Gb is 4.6Mb!

 

However, this could vary - does the usage go up when your web server kicks in?

Has the bad performance of the web server gone away?

 

I think we determined that the server has just 1GB of main memory. My gut feeling says this is rather low - the OS has to fit in there plus the application plus buffer space.

A server that swaps send your performance down the tubes. Since memory is generally cheap - I'd suggest doubling it.

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Hang on, your on a VM? and not a real machine? (checks pdf - virtual memory, not virtual machine)

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Linux will always use a swap file if there is one. That's just the way the algorithms are written.

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Don't get the server load thing. It's red, but load is normally measured in % and it says 2.31. Odd. Is it behaving at the moment?

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if it never needed the SWAP file...why is it now using it then???

As wheel says that's just the way Linux works. If your server has only 1Gb of memory then it's a bit low and the simple thing to do is double it (or even better expand it to 4Gb depending on what your server can take and the price of the memory), it's cheap, and less hassle than changing the hard disk, and will probably make all your problems go away.

 

Edit: And if you're only using this as a server then you probably don't need a GUI - try 'init 3' and see if things run more stable.

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Thanks for looking peeps but I think I have been mentally broken and am going for the sledgehammer to crack this walnut.

 

As the server is a monthly managed dedicated solution I am gonna upgrade to a shinier, fastier server and reload sites one by one. I get 2 weeks to migrate anyway.

 

Bit of a drag, but I know what I am doing shifting the sites across and its much less painful than the current dramas. End effect I will get a better server with RAID etc.

 

I am *optimistic* that whatever the problem is, it will not follow me to the new server.

 

The bit that makes me shudder is actually shifting the domains (as this normally cocks up 'cos they dont set the nameservers up correctly) and the worst of all is shifting

SSL certificates - normally easier to buy new from scratch!!

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As the server is a monthly managed dedicated solution I am gonna upgrade to a shinier, fastier server and reload sites one by one. I get 2 weeks to migrate anyway.

CPU speed is not necessarily the most important matter - memory! In your shoes I'd still try additional memory first.

 

If you are really going for a new server consider a "Cool Thread" 64-thread T5120 server from Sun (supposedly great for parallel web access). :)

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JE: Free memory on Unix usually means: Used for the buffer cache. You need a big buffer cache for decent IO performance. VMs and Schedulers are quite advanced on Unix, their algorithms probably concluded that your programs need a lot of IO cache and that there's certain parts of your application that are not used much so they can be swapped.

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