Performance
Overview
AutoSave can cause a significant load and thus lag upon a server as it performs its saves. By default, Version 3 and on will use Synchronous file saves to prevent unexpected errors from occurring while the game operates. It is still possible to use Asynchronous mode, but this mode should be used with caution and only if one understands the effects it will have upon your environment.
Interval Times
A reasonable interval time should be choosen to prevent frequent delays upon a server. On small servers, saving every few minutes isn't a problem and likely not noticeable. However on large servers, it is wise to provide a longer interval between saves as each save may cause a significant lag effect. Suggested default values for saves on large servers are around the half hour to hour mark depending upon your environment and desire to ensure the least impact a crash may have upon your server.
Multi-world
If you have multiple worlds, it is advised to consider removing worlds (see the commands page for information on how to configure the worlds) as to not cause unnecessary lag for worlds which may be less important. It is common to see servers ignore their Nether worlds.
Saving Mode
AutoSave Version 3.0.0 and up will have a configuration for the saving mode. Synchronous mode performs a save blocking the Minecraft server from performing other operations whereas Asynchronous mode does not.
Synchronous Saving
Synchronous saves cause the server to wait for the operation to finish before processing other code during a tick. This works well except that performing world saves commonly take longer than the time given between ticks which is the cause for the lag like effect. The benefit of using Synchronous Saving modes is that the default Minecraft chunk saving system can remain turned on and chunks will be saved per the Minecraft server logic.
Asynchronous Saving
Asynchronous saves allow the server to continue to perform other operations while the server also is saving the world. This mode requires disabling of the internal Minecraft automatic saving functionality and as such the only Saves which happen are then only AutoSave. This mode dramatically improves performance and the lag effect that can be found in Synchronous mode vanishes. However, with this method also means that if you infrequently save, crashes may revert your world further behind than had you used Synchronous Saving. However, given that the lag is reduced on is possible to decrease the interval between saves depending on your hard drive speeds. This is recommended for large servers where Synchronous mode can cause significant lag issues.