When you first encounter LiteSpeed Web Server (LSWS), choosing the right license or even the right LSWS edition can be difficult. This wiki will explain the differences between different editions and licenses (focusing more on licenses) and then go over some ways to help decide which license is right for you.

There are three different editions of LiteSpeed Web Server. (See the feature comparison on the main site for an in-depth comparison.)

• Standard Edition: Free. Meets the needs of small websites. Automatically reads and uses Apache configurations, but has a limit of 150 concurrent connections and up to 5 Apache vhosts.
• OpenLiteSpeed: Open source and free. Powerful enough for any website, but does not automatically read and use Apache configurations. Easy to configure (understands Apache mod_rewrite syntax), but requires that you configure it on your own.
• Enterprise Edition: The ultimate combination of power and usability. Even more power and features than OpenLiteSpeed. Faster than any other major web server. Requires almost no set up because it automatically reads and uses your existing Apache configurations (including .htaccess files). Compatible with cPanel, Plesk, DirectAdmin, and Interworx and almost all web applications.

LiteSpeed Web Server Enterprise Edition has 6 different licenses to choose from. These licenses reflect how much power LiteSpeed Web Server will be given. Generally, the licenses are divided by how many cores LSWS will have access to, though there are two special, more affordable licenses only for VPSs.

• VPS Licenses: An affordable option for a smaller VPS. The VPS license has a limit of 500 concurrent connections and 2GB RAM. The VPS license has access to one core on your server.
• Ultra VPS Licenses: A solution for VPS users who have between 2GB and 8GB of RAM. The Ultra VPS license has a limit of 800 concurrent connections. VPS users with more than 8GB of RAM will require a 1-CPU license. (The Ultra VPS license is only supported on LiteSpeed Web Server v4.2.2 and up.)
• 1-CPU, 2-CPU, 4-CPU, and 8-CPU Licenses: All other licenses are differentiated by the number of cores they are allowed to make use of. The number of CPUs in the license title refers to the number of the server's cores that LSWS will be able to make use of. Thus a 1-CPU license has access to one core, and a 2-CPU license has access to two cores, etc. Note that you do not need to have LSWS make use of all your server's cores. (See below.) LSWS is fast and lightweight enough to run very, very well on only a fraction of the server's cores.
• LSCache:

Notes: VPS and Ultra VPS licenses will not install on a dedicated server or a VPS over their respective RAM limits. If the concurrent connection limit is surpassed, extra connections will be queued until there is room in the connection limit. Currently supported VPS platforms are KVM, HyperV, Virtuozzo, OpenVZ VPS, XEN, VMWare and UserModeLinux VPS.

A license does NOT require the licensed CPU cores to match the amount of CPU or cores of your physical server. It simply denotes the number of CPUs that the LiteSpeed server process utilizes. LiteSpeed web server itself is very lightweight and does not consume as much CPU or memory as MySQL and PHP does.

If your server has more than one CPU core, you may choose between 1, 2, 4 or 8 CPU licenses. If you have a very powerful server with several dozens of CPU cores available, please contact sales for customized build solutions.

Note:

1. HyperThread does NOT count.
2. You may get 2-CPU license for 1 CPU server if you need cache functions (not available for 1-CPU license).
3. You may get a license that matches up server CPU cores for a heavy file download server. IOW, have LSWS fully utilize server CPU power.

Some factors to consider:

• What other processes are running on the same server?

For example, if you have a 4-core server and run LSWS, PHP, and MySQL on the same server, you can buy 1 or 2-CPU license, as your other CPU power will be fully utilized by PHP and MySQL processes. Usually for a 4-core server, you will not need anything higher than a 2-CPU license if you have other external applications like PHP or RoR.

• Do you have a high volume of HTTPS traffic?

This requires more CPU power for encryption.

• Is the content you serve mainly static (such as images, file downloads, etc.)?

These are served by LSWS directly, so more CPU will help. If your server is mainly PHP/MySQL powered, a 4-CPU license may not help much as LiteSpeed will not be the bottleneck.

• What is 'disk I/O wait?'

Like all other lightweight web servers, blocking disk I/O will block LiteSpeed's process. Therefore, if your server has high I/O wait, you should consider a higher CPU license in order to compensate. Since version 4.1, LiteSpeed has supported AIO (asynchronous IO).

• LiteSpeed Dynamic Content Cache, a varnish-like page cache, is only available for 2-CPU licenses and onwards.
• VPS licenses cost less, but have restrictions of 500 concurrent connections and a 2GB memory limit.
• Ultra VPS, with restriction of 600 concurrent connections and an 8GB memory limit, has been available since March 2013.

There is limit for max concurrent connections for different licenses. The free version has a limit of 150, the VPS license, 500, Ultra VPS, 600, and the Enterprise edition is unlimited. You can check the number of concurrent connections used from the real-time report under web admin console, or use the command

netstat -an | grep 80 | grep ESTA | wc -l 

Remember, though, only “established” connections from netstat output are considered to be concurrent. For example, a forum with 3,000 users online might only use 300 concurrent connections, as those 3,000 users do not all execute actions at the exact same split second.