lpoulain / sawa

Samba Wannabe, a network filesystem on Linux

SaWa (Samba Wannabe)

SaWa is networking filesystem on Linux. It is composed of two pieces:

• A file server running in userspace which is accessible through TCP port 5000 (port 5001 for administrative commands)
• A block driver, which acts as the client and talks to the server through TCP/IP

The file server

The fileserver listens to port 5000, uses a flat file for the filesystem and accepts four commands:

• Info, which returns the number of sectors

• Read, which reads a certain number of bytes

• Write, which writes some data at a certain offset

• Stop, which stops the server

  $ ./server/sawad [-debug] Server started on port 5000

To test the fileserver, sawa-client is also provided:

$ ./server/sawa-client info
$ ./server/sawa-client write 10 100
$ ./server/sawa-client read 10 100
$ ./server/sawa-client test 3
$ ./server/sawa-client stop
$ ./server/sawa-client stat

The device driver

The device driver is a Linux block driver which connects to the file server using TCP/IP (currently only on localhost) when it needs to access the data. See here for further information about how the device driver works.

You must be logged as root to install and test it:

• make
• make test: installs the driver
• fdisk /dev/sawa0: creates a partition
  • Enter n (to create a new partition), select all default options
  • Enter w to commit the changes
• mkfs /dev/sawa0: formats the filesystem
• mount /dev/sawa0 /mnt: mounts the filesystem

After this the filesystem is available, e.g.

# cd /mnt/
# echo "Hello World" > hello.txt
# cat hello.txt

To uninstall the driver:

• umount /mnt: unmounts the filesystem
• make end: uninstalls the driver

Web Server

sawad is designed to handle multiple connections (using different threads). In order to test how well sawad handles workload, it has an -http option which turns it into a rudimentary Web server, so it can be tested by tools such as ab.

./server/sawad -http
./server/sawad -http -debug

ToWa (Tomcat Wannabe - in construction)

On top of being a Web Server, sawad can also be the frontend for the ToWa Application Server, servicing Java servlets.

This module is in construction and is barely working at this point. It requires several things to work properly:

• Copy servlet_api.jar to the classpath folder. ToWa has been tested with OpenJDK 1.6 and servlet_api.jar version 3.0
• Start sawad -http -towa
• Call [http://127.0.0.1/Test?doesitwork=yes] to call the Test servlet
• Call [http://127.0.0.1/Kaboom] to see what happens when an exception occurs in the Java code

Architecture

• Block Driver architecture
• SaWa Server architecture
• The client/server TCP protocol
• ToWa architecture