The Most Common Causes of Downtime
Website downtime damages your sales and your reputation as well as losing you customers. It is vital to your business that you minimise downtime as much as possible and to do that, you must first know your enemy.
Identifying the potential causes of downtime to your site helps you to minimise the threats and also prepares you to deal with the problem more efficiently when downtime occurs.
Downtime can be classified into two types - hard downtime and soft downtime.
Hard downtime is when the website becomes completely unavailable to users. Trying to access the website during hard downtime will direct users to dead pages, pages with HTTP errors or even to malicious content if the site has been hacked.
Soft downtime is when the website is affected by poor performance, such as when it takes a long time to load and/or parts of the site or content are inaccessible.
So why do websites go down?
Downtime can be due to problems with a website itself, with the server that hosts it, with servers in between the User and the host, or because of DNS errors. The causes of downtime vary between websites/servers but here are some of the most likely culprits:
- Human Errors are thought to be the biggest causes of system downtime. Mistakes such as unintentional file deletion (404 Error) can play havoc with your uptime.
- Coding Errors are another common reason your website would be inaccessible. Infinite loops, incorrect syntax, typos could all cause a server to exhaust it's resources yielding 500 (Internal Server) error codes.
- Database Server Errors such as corrupted tables, database server shutdowns, dropped or missing tables, requests for non-existent columns, unquoted values, would cause dependant server side scripts (PHP, CGI, ASP, etc.) to either partially or fully fail.
- Inefficient Database Processes backed up due to heavy processing would also cause dependant server side scripts (PHP, CGI, ASP, etc.) to fail and website outages.
- Exhausted resources including hard drives with no more space for data to be written to and Physical and Swap memory exhaustion will definitely bring a server down or truncate web pages resulting in only a portion of a web page being displayed.
- Apache/HTTP Server Timeouts will results in a server 500 error, making your website unavailable. This occurs when a process (spawned by a server side script) exceeds the allowed time for the process to complete. Default Apache Timeouts range from 120 seconds to 300 seconds.
- Malicious attacks from hackers or viruses can take your website offline, hi-jack your website or redirect visitors to malicious content or other websites.
- A webs server would come crashing down in the event of Hardware Component failure. An aging hard drive or RAM, even a an over-worked fan at the end of it's life can all cause downtime.
- Natural Disasters such as earthquakes, floods, fires, etc. can potentially have a devastating effect on hardware, although most modern data centers are disaster and bomb proof.
- Planned downtime may see a 503 (Service unavailable) error returned. Every now and then you or your web host must do some essential housekeeping like installing upgrades for hardware, software or operating systems, or transferring to a new webhost and all of these will take your website offline. There's no guarantee every page on every website will be checked after an upgrade and the host may assume everything's OK after checking just a few sites.
- Bad Gateway errors occur when there's a communication failure between servers. The User's connection may be OK, and the website server may be OK, but a server in the chain of hops between the client and server is failing to understand a response.
- Spikes in Traffic, be it legitimate traffic or DDOS attacks, would result in extremely slow response times or no response at all.
- Fatal Directives in .htaccess files often cause websites to go down. One incorrect or mis-understood directive could result in and infinite redirect loop, 401 (Unauthorized Access), 403 (Forbidden Access) and 500 (Internal Server) errors.
- Your website may go down because of incorrect permissions either on folders or files will result in 403 (Forbidden Access) or 500 (Internal Server) error code.
- Gateway errors (504 Gateway Timeouts) will make your website inaccessible. These are errors occur when one server doesn't receive a response from another in a timely manner.
- Ports Closed or filtered Ports will block traffic to your website. Your server will be fully functioning, but no-one will be able to reach it.
- DNS errors which can be caused by either the host or the website owner playing with the DNS settings in their control panel, or may even be because the registrar deliberately shut down DNS for the website dues to the website owner not responding to their requests for contact. ICANN (Internet Corporation for Assigned Names and Numbers) now requires website owners keep their WHOIS information regularly updated and accurate. If you've changed the email address you provided to your registrar and they can no longer contact you, you may find your website has been taken offline.
- Expired Domain Names will see your website taken offline. If you're not careful, you may even lose your domain name permanently to the domain name thieves who have programs set up to pounce on domain names the moment they become available. Sign Up with SiteStillUp to have SMS reminders sent to you when your domain name is about to expire.
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