6.824 - Spring 2012

Lab Information

Lab overview

In this sequence of labs, you'll build a multi-server file system called Yet Another File System (yfs) in the spirit of Frangipani. At the end of all the labs, your file server architecture will look like this:

You'll write a file server process, labeled yfs above, using the FUSE toolkit. Each client host will run a copy of yfs. Each yfs will create a file system visible to applications on the same machine, and FUSE will forward application file system operations to yfs. All the yfs instances will store file system data in a single shared "extent" server, so that all client machines will see a single shared file system.

This architecture is appealing because (in principle) it shouldn't slow down very much as you add client hosts. Most of the complexity is in the per-client yfs program, so new clients make use of their own CPUs. The extent server is shared, but hopefully it's simple and fast enough to handle a large number of clients. In contrast, a conventional NFS server is pretty complex (it has a complete file system implementation) so it's more likely to be a bottleneck when shared by many NFS clients.

Lab assignments

Lab 1 - Lock Server
Lab 2 - Basic File Server
Lab 3 - MKDIR, UNLINK, and Locking
Lab 4 - Caching Lock Server
Lab 5 - Caching Extent Server + Consistency
Lab 6 - Paxos
Lab 7 - Replicated lock server
Lab 8 - Project

Collaboration Policy

You must write all the code you hand in for the programming assignments, except for code that we give you as part of the assignment. You are not allowed to look at anyone else's solution, and you are not allowed to look at code from previous years. You may discuss the assignments with other students, but you may not look at or copy each others' code.

Programming Environment

You should be able to do Lab 1 on any Unix-style machine, including your own Linux/FreeBSD desktops, MacOS laptops, or any Athena SunOS/Linux workstation.

For Labs 2 and beyond, you'll need to use a computer that has the FUSE module, library, and headers installed. You should be able to install these on your own machine by following the instructions at fuse.sourceforge.net; we outline instructions for Ubuntu/Debian machines. However, the official programming environment for this class will be the Athena Linux machines (you can find a list of Athena Linux workstation locations here). What we mean by official is that we will be testing your assignments using that environment, so please make sure your code passes the tests on an Athena Linux machine.

Note that if you have your own FreeBSD or MacOS machines that you prefer to use for programming, you should be able to use them for the majority of the work. However, there are minor annoying differences between FUSE on Linux and FUSE on other operating systems that may cause your code to fail our tests when it seems to pass for you. As an example, on Linux FUSE passes file creation operation to the file system using the MKNOD call, while on other systems it uses CREATE. Please ensure that your assignment passes the tests in the Athena Linux environment, and there shouldn't be any problems when we test it.

Athena Linux Machines Without FUSE

Some Athena Linux workstations do not have FUSE installed on them by default. We have created a 6.824 locker that includes all the necessary FUSE files, as well as installation scripts. Note that you must be root to run these scripts. To install FUSE on an Athena Linux workstation, do the following:

% attach 6.824
% tellme root
% su -
  [Now enter the root password shown in the previous command to become root]
% /mit/6.824/install-fuse.sh
% exit

Now you should be able to compile your FUSE-based programs and run them without any problems. When you are finished with a session and are about to log out, MIT asks that you please clean up after yourself by uninstalling the FUSE programs. Do this as follows:

% tellme root
% su -
  [Now enter the root password shown in the previous command to become root]
% /mit/6.824/uninstall-fuse.sh
% exit

Installing FUSE on Ubuntu/Debian

To setup FUSE on your local machine, you will need the header files and the utilities. Install them like this:
sudo aptitude install libfuse2 fuse-utils libfuse-dev
Next, you need to make sure the fuse module is loaded:
% ls -l /dev/fuse 
  crw-rw-rw- 1 root fuse 10, 229 2010-02-11 06:02 /dev/fuse
If your ls output matches the above output, then you can skip the modprobe step. If you do not see the above output, try running modprobe:
% sudo modprobe fuse
Finally, you need to add yourself to the fuse group to be able to mount FUSE file systems:
% sudo adduser {your_user_name} fuse
Make sure to logout of you current session to refresh your group list. When you logged in again, typing groups at the command line should show fuse as one of the groups:
% groups
  alex users fuse admin

Aids for working on labs

There are a number of resources available to help you with the lab portion of this course:

Questions or comments regarding 6.824? Send e-mail to 6.824-staff@pdos.csail.mit.edu.

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