1 Introduction

This document gives a short introduction to installing and compiling the log-structured prototype (LLD) of the Logical Disk (LD). The Logical Disk defines a new interface to disk storage that separates file management and disk management. The LD interface is designed to support multiple file systems and to allow multiple implementations, both of which are important given the increasing use of kernels that support multiple operating system personalities. The log-structured prototype of LD is based on the assumption that most reads are absorbed by the file system cache and that therefore disk traffic is dominated by writes. LLD writes dirty file system blocks to disk in long contiguous writes. It divides the disk into large, fixed-size segments; the segment being filled is maintained in main memory and written in a single disk operation.

We have implemented LLD as a user-level process and linked it to the Minix file system (MinixLLD). MinixLLD can use a file or a raw disk partition to store data. It runs on Sun workstations running SunOS 4.1.3, but we expect that LLD will run on most BSD-like operating systems with minor changes.

MinixLLD is intended as a file system for experimentation and evaluating research questions. It is not ready to be used as a production file system. We can not make any guarantees in any way.

The following research papers discuss the Logical Disk, the log-structured prototype and atomic recovery units (a mechanism that allows several disk operations to be executed as a single atomic unit with respect to failures):

• Wiebren de Jonge, M. Frans Kaashoek, and Wilson C. Hsieh. The Logical Disk: A New Approach to Improving File Systems. In Proceedings of the 14th Symposium on Operating Systems Principles, pages 15--28, 1993.
• Robert Grimm, Wiebren de Jonge, Wilson C. Hsieh, M. Frans Kaashoek. Atomic Recovery Units: Failure Atomicity for Logical Disks. To be published.

The rest of this document is structured as follows: Section 2 gives an overview over the source tree and highlights some important compiler flags and source files. Section 3 describes the steps necessary to compile LLD. Section 4 describes how to run LLD. This document assumes that the source distribution for the Logical Disk has been downloaded, uncompressed (using gunzip ld-1.0.tar.gz) and untared (using tar xf ld-1.0.tar). All directory references in this document are relative to the top-level directory for the source distribution. The source distribution and related documents can be accessed through the world-wide web at http://www.pdos.lcs.mit.edu/ld/.