4GB VPS Keeps Freezing with nearly 100% CPU Usage

[sm9]

Hi there,

I have a VPS with 4GB ram and running WHM/cPanel 11.24.

It only has one website running on it and it isn't getting more than a few hundred visitors a day so traffic shouldn't be an issue, but a few times per week, the website is either freezing or being very slow to load for a period of of several minutes or more.

I've called the web host a few times when this has happened, but besides telling me that the CPU load is running at nearly 100%, they can't figure out what is causing this, and the error_log and access_log aren't giving any clues either.

Is there anything that can be installed on the server that should give us some more meaningful information to track this down at all? Or is there anything I should be checking in particular?

Besides the website, the server is also hosting the POP3/SMTP emails for the client but they don't seem to be getting too much traffic and the mail queues are empty.

Any advice would be appreciated.

Thanks,

Stephen

[Spiral]

It's highly doubtful that a VPS would actually really have 4 GB of Ram assuming also that you do in fact really have a VPS server ...

However ignoring that, what OS and kernel is the underlying hardware running
and what is the VPS node running?

Do you know what virtualization platform is in use?

While it is worthwhile to look into your system logs as you have clearly already done trying to source out the problem, do not ignore that the memory, network, and processor is being shared by all VPS server accounts hosted on the same physical machine as your VPS server account so it very well could be another server bringing yours down as well.

I very strongly do not recommend traditional VPS servers in any case as they are already prone to major performance and reliability problems and inherent security issues, some of which cannot be repaired or closed by any means.

[sm9]

I'm using one of these: VIRTUAL SERVER | DEDICATED VPS | VIRTUAL SERVERS : MEMSET - the VM8000. So yes, it's a VPS and has 4GB RAM...

Apparently, it uses Xen but I don't know any more about this other than what's on their website.

If you don't recommend traditional VPS servers, what do you recommend instead?

And back to my question, can you or anyone else recommend any software to install on the server or within WHM/cPanel that might tell me what's using all this processing power when these spikes are happening?

Thanks,

Stephen

[Infopro]

CSF can help with this depending on how strictly you set it up.
ConfigServer Security & Firewall

[Spiral]

I'm using one of these: VIRTUAL SERVER | DEDICATED VPS | VIRTUAL SERVERS : MEMSET - the VM8000. So yes, it's a VPS and has 4GB RAM...

Apparently, it uses Xen but I don't know any more about this other than what's on their website.

If you don't recommend traditional VPS servers, what do you recommend instead?

And back to my question, can you or anyone else recommend any software to install on the server or within WHM/cPanel that might tell me what's using all this processing power when these spikes are happening?

Thanks,

Stephen

Well I can tell you one thing right from the sales page you just quoted ....

10Mbps 40:1

That number says that your only amount of guaranteed bandwidth would be 256Kbps which would be split by all your connections and all your users you have on your server at any given moment.

(Which isn't exactly rocket science to figure out that is hideously slow)

If more bandwidth is available, you might be able to go a bit faster, but it's not going to necessarily be available so you'll likely see severe fluctuations in your network performance at various times and net loads.

Now regarding the 4 GB question, I am not really asking about what limit they set for your server rather as how much would actually truly be available which for VPS server is typically actualized roughly around 30% to 45% of the set dedicated limit and even less of the burstable (shared) resources.

Or to put that into plain English, if you have an average VPS server with say 1 GB of memory guaranteed burstable to 4 GB, in reality you may only be getting actual real access (usage) to roughly 700K of memory if that and some of that is going to further going to be taken away by the virtualized system itself leaving you even further reduced.

(Incidentally the above is why low end budget dedicated servers typically run performance circles around high powered VPS server accounts)

You asked what I would recommend?

Either a Dedicated or Cloud / Cloud VPS server

And at this point, you are probably looking at that statement and are a bit puzzled. Don't be!

Cloud servers, though based on a similar principle, as VPS servers are a totally different technology entirely. Where traditional VPS servers split the resources of a single machine, cloud technology goes further and virtualizes servers from the resources of a large network of physical servers working in tandom as a huge super-computing cloud. This gives incredible fault tolerance and relibility that can't be matched by any other technology and in a true cloud archatecture, leave near perfect immunity to the thread of hardware failures, and more importantly since the resources of multiple machines can be allocated on demand, you can actually have full access to the network, processor, and memory resource you are allocated and not fight over who get's to the cpu core at whatever particular clock cycle any given second but stream that to the next available core on standby.

There are currently only a small handful of true cloud providers and most of those actually market themselves as VPS server providers because cloud servers, though technically superior to dedicated in some respects, can be priced competitively against traditional VPS servers and so that is the market which most of these providers focus. This number is growing rapidly and cloud technology is the next generation server platform and public interest is continuing to grow at an exponential rate (just check google trends) or do a few searches on "cloud computing" and you'll see quickly what I mean.

There is another type of "transitional" server out there as well which is being marketed as both "cloud" sometimes and sometimes as "vps" to make things even more confusing for the consumer market and that is a hybrid cloud which basically in a nutshell pulls a little bit of the concepts of cloud and non-cloud such as using cloud virtualization but standard server hard drives or a clustered environment with standard VPS servers allocated to the nodes of the cluster, etc.

Meanwhile, I have seen a number of traditional VPS server providers actually market themselves as "cloud" to try to take advantage of the cloud popularity even though they are in reality just standard VPS server providers.

Eventually public awareness will likely rise to the point where they will no longer be able to blur the lines and exploit the confusion for consumers

Looking totally on the other side of the coin -- dedicated. For 80 pounds a month (the quoted price of your account), you could easily get yourself a cozy dedicated that would drastically outperform your current VPS server.

Hope that helps

[Infopro]

While I'm not so sure I understand what all of the above has to do with the original post, my suggestion is a valid one still.

CSF can help with this depending on how strictly you set it up.
ConfigServer Security & Firewall

CSF can be configured to kill off an out-of-control process and email you details on it.
Your question:

Is there anything that can be installed on the server that should give us some more meaningful information to track this down at all? Or is there anything I should be checking in particular?

Yes. See link above. A snip from that page:

•Alert when end-user scripts sending excessive emails per hour - for identifying spamming scripts
•Suspicious process reporting - reports potential exploits running on the server
•Excessive user processes reporting
•Excessive user process usage reporting and optional termination
•Suspicious file reporting - reports potential exploit files in /tmp and similar directories
•Directory and file watching - reports if a watched directory or a file changes

So when this happens:

a few times per week, the website is either freezing or being very slow to load for a period of of several minutes or more.

..you'll have more reporting at your fingertips to work with so you can track the problem down.

I'm sorry I didn't provide more details to begin with in my original post. The details at that link do speak for themselves though.

[SoftDux]

@spiral,

I think you are a bit misinformed about XEN VPS's & memory usages. On a XEN VPS, the full 4GB RAM that the OP was given, is his. His VPS doesn't share any RAM with any other VPS.

The problem probably lies somewhere else though.

@Stephen,

Which version of cPanel & WHM are you running?
Which versions of Apache, PHP & MySQL are you running?
What scripts are running on the website? Are they common downloadable scripts like Joomla / SMF / etc, or is it custom build?
Are the scripts up to date?
What is the output of top?

[Tam]

Please post the output of

cat /proc/user_beancounters

[SoftDux]

Please post the output of

cat /proc/user_beancounters

XEN VPS doesn't have a /proc/user_beancounters.


Why does everyone automatically assume that if someone has a VPS, it's a) crappy, and b) on virtuzzo / OpenVZ??? There are other, better alternatives to OpenVZ - which doesn't crash at an instant, and isn't affected by the load of other VPS's on the same server.

[Tam]

XEN VPS doesn't have a /proc/user_beancounters. Why does everyone automatically assume that if someone has a VPS, it's a) crappy, and b) on virtuzzo / OpenVZ???

That's a really useful reply (full sarcasm intended).

For the OP, post the output of

ps axfuw

during this high load.

[sm9]

Hi guys,

Thanks for the replies and sorry for not replying back sooner.

I no longer have this 4GB VPS as the period of peak traffic ended. However, I found this particular VPS problematic with these issues right until the end, with the web host denying any issues were at their end.

This VPS was setup in exactly the same way as a 1GB VPS that I'm using with the same web host, with the same cPanel account in it, and it's been absolutely fine since we moved the website back to that and even had a period of high traffic without issue.

I can only assume that there was some sort of issue with that particular 4GB VPS or host server. Needless to say, I wasn't happy and won't be getting a 4GB VPS from this web host again.

Stephen