Changes between Version 36 and Version 37 of FAQ

Timestamp:

2016-02-17T14:34:04Z (8 years ago)

Author:

Jakub Jermář

Comment:

—

FAQ

@@ -6 +6 @@
 === What is a microkernel? ===
 
-In a microkernel operating system certain functionality such as device drivers, file systems and networking is moved out from kernel space to user space. The microkernel itself provides only minimal functionality that is necessary for user processes to run and communicate. This strongly contrasts with the traditional monolithic operating systems that keep most of these functions inside the kernel. The main rationale for designing operating systems along the microkernel lines is that a bug in a kernel driver of a monolithic operating system usually results in the crash of the entire system whereas a bug in a user space driver of a microkernel operating system is confined to the user process in which the driver runs.
+In a microkernel operating system certain functionality such as device drivers, file systems and networking is moved out from kernel space to user space. Code taken out of the kernel runs as a normal user process or processes. The microkernel itself provides only minimal functionality that is necessary for user processes to run and communicate. This strongly contrasts with the traditional monolithic operating systems that keep most of these functions inside the kernel. The main rationale for designing operating systems along the microkernel lines is that a bug in a kernel driver of a monolithic operating system usually results in the crash of the entire system whereas a bug in a user space driver of a microkernel operating system is confined to the user process in which the driver runs.
 
 === What is a multiserver? ===
 
-Within the scope of microkernel operating systems, a multiserver system spreads the operating system functionality over multiple user processes. Note how this is different from a single-server microkernel that concentrates all these functions into a single user process.
+Within the scope of microkernel operating systems, a multiserver spreads the operating system functionality over multiple user processes. Note how this differs from a single-server microkernel that concentrates all these functions into a single user process. The motivation for structuring the system as a multiserver is the elimination of the single point of failure represented by the single server process in a single-server system. Another advantage of a multiserver system is smaller and simpler components that can communicate only via explicit interfaces. Smaller and simpler components benefit from the separation of concerns, can do one thing really well and are easier to reason about. Explicit interfaces make the components interchangeable and the correctness of the system on the component-granularity level is easier to reason about. At the same time, it is more difficult to use the component in a wrong way.
 
 == General HelenOS Questions ==