Linux Hosting Resource Limits
Posted by on 03 December 2014 10:34 PM
* To avoid confusion and frustration, we want to ensure the limitations of our different hosting packages are clearly defined. This is expanding on our existing "how limited is unlimited" article which can be found here: https://support.arvixe.com/index.php?/Knowledgebase/Article/View/129/4/how-limited-is-unlimited . If your account is on a CentOS5/1h/Hive server, please see the article at https://support.arvixe.com/index.php?/Knowledgebase/Article/View/192/4/resource-usage-explained .
Linux Hosting Resource Limits
Very high amounts of resource usage may require immediate action to be taken on your account to provide immediate relief (such as disabling the script, etc). If this happens, you will be contacted by one of our system administrators via email. We do not currently have tools to make monitoring of your Windows hosting account resource usage possible.
Our next generation linux hosting platform is built on CentOS 6 with CloudLinux, which allows us to better define and manage real time access quotas to shared resources so as to avoid the necessity for manual intervention.
This article will outline and detail those limits.
Access quotas to shared resources are automatically applied based on the hosting plan in use. By providing controlled and fair access to these resources, the likelihood of a single account impacting the performance of other customers on a shared server is greatly reduced. The various plans and their limits are in the table below:
CPU: Each server has between 16 and 40 CPU cores, with each core represented in the above chart as 100%. Even though the kernel may distribute usage across multiple physical CPUs, usage is calculated as a percentage of the total CPU seconds per core per second.
Memory: The amount of physical RAM that can be used by your hosting account at any given time. Most accounts will never use more than 128MB, but all of our plans allow ample room for multiple sites or larger applications.
Virtual Memory: The amount of virtual and/or reserved memory available to your hosting account at any given time. This is in addition to the physical RAM where your applications actually run. Most applications will reserve memory that they never actually use. This "virtual" memory space is counted seperately from actual RAM usage along with any virtual memory mechanisms that your application may employ.
Entry Procs: The number of processes with active connections through apache at any given time. This is not a cap on connections to the websites under any given account, but a limit on the number of scripts actively delivering content to apache at any given moment. To give an example, a limit of 50 might equate to 50 visitors streaming videos through your site or 500 visitors clicking around your blog.
Total Procs: The maximum number of processes that can run under your hosting account at any given time. This includes entry procs.
IO: The maximum disk IO speed for your hosting account. This is how much data you can read and/or write per second. This does not include MySQL data.
From within cPanel, you can see your usage statistics in the left hand column:
These statistics should refresh on ever page load.
For historical details, you can access 'Resource Usage' under the Logs section:
If your account has attempted to exceed any limits, you should be presented a notice like this:
You can then examine the details to identify any spikes or abnormal usage over various periods. Normally such spikes will correlate with abnormal patterns in your access logs that you can use to identify and block unwelcome traffic:
Details are provided in both graph and table format for ease of use and portability:
Visiting a limited site:
When visiting a website that is currently being limited, you will receive various errors like 500, 508, 408, depending on things like which limit is being exceeded and how your script reacts to that limit being imposed. If the issue persists for unacceptable periods of time, it is a sign that it is either time to upgrade to a plan with more resources, or that you need to identify and control overzealous/abusive/malicious traffic. The access logs for the account will indicate which it is, and you can use the 'IP Deny Manager' under the security section of cpanel to help block the unwanted traffic.
SERVERS CAN NOT BE USED FOR MAILING LISTS/BULK MAILING.
MySQL queries are currently limited only by IOPS, but upgrades are rolling out that will move MySQL processing into the userspace, thereby reducing one of the major remaining sources of poor performance on a shared server.