CloudLinux improves the stability of a server by limiting each client in an isolated, secure environment called a Lightweight Virtual Environment (LVE), a kernel technology developed by CloudLinux.
In shared hosting, the most common reason for downtime is a single account slowing down other accounts on the server. If one customer is using an unfair amount of resources (e.g. due to being under a DDoS attack, poorly written script, etc.), the server would become slow or go down completely, affecting all other customers on the server.
With CloudLinux, we are able to isolate the impact to the offending tenant only, while all other sites remain unaffected. CloudLinux improves the general stability and performance of the server by imposing limits on the number of resources that can be consumed by a single user.
When an account hits the LVE limits allocated to it, a snapshot is generated allowing you to see which processes are responsible for those limits being hit and can be reviewed from the 'Resource Usage' section of cPanel.
Also, we now send alerts when an account hits the LVE limits, so that you can be informed if an account has performance issues, code issues or potential malware or if the account simply requires more resources via an upgrade.
The first step is to review the 'Resource Usage' screen in cPanel, and see if you can trace what processes were responsible for the high usage at the time.
From there, the solution would depend on the root cause but is typically an issue at application level such as poorly written PHP scripts, outdated or poor quality plugins, larger numbers of plugins or even potentially malware.
As a hosting provider we are responsible for the hosting infrastructure, as opposed to the applications that run within the hosting platform so we are unable to diagnose PHP related issues or problems via support - therefore it may be best in some cases, to reach out to a developer for further assistance.
If the account resource usage is genuine requirement, and is just a 'resource heavy' site then the best course of action would be to upgrade the account to a more suitable plan, such as our Premium Hosting.
If you are a shared hosting client, you will be informed by email from email@example.com
If you are a reseller, you will be informed of the LVE faults for any of the sites directly by email which will come from firstname.lastname@example.org
This email will outline the number of 'faults' (the number of times the LVE has been hit), along with the accounts affected.
Please note, that for the benefit of white-labelling, we do not at present send notifications to your customers directly.
We will send usage alerts for any accounts hitting their LVE limits every 12 hours.
As some of the LVE restrictions only 'slow down' a site, as opposed to taking a site entirely offline we don't notify for every individual fault.
Instead, we send notifications if an account exceeds its limits more than 100 times spanning the 12 hour period.
If an account is only receiving a small number of LVE faults, and the its mainly surrounding CPU usage or IO, the chances are that there would be no implications at all, other than a slow down of the site during these fault periods.
However, if you have accounts which are exceeding the resource limits 'excessively', we reserve the right to suspend an account to prevent further resource consumption.
We will suspend an account if it receives more than 5000 LVE faults in the space of 60 minutes.
The reason for this, is that 'SIGKILL' is a kernel process which is called at the point of an LVE fault occurring (which is what triggers the 503 error). This process itself can have negative impacts on the servers performance and stability overall when called simultaneously over short periods of time.