operating system version. Thus, DEC OSF/1 v3.2 had AdvFS v2.x, Digital UNIX 4.0 had AdvFS v3.x and Tru64 UNIX 5.x had AdvFS v4.x. It is generally considered that only AdvFS v4 had matured to production level stability, with a sufficient set of tools to get administrators out of any kind of trouble. The original team had enough confidence in its log based recovery to release it without an "fsck" style recovery utility on the assumption that the file system journal would always be allocated on mirrored drives. In 1996, Lee and Thekkath described the use of AdvFS on top of a novel disk virtualisation layer known as Petal. In a later paper, Thekkath et al. describe their own file system (Frangipani) built on top of Petal and compare it to the performance of AdvFS running on the same storage layer. Shapiro and Miller compared the performance of files stored in AdvFS to Oracle RDBMS version 7.3.4 BLOB storage. Compaq Sierra Parallel File System (PFS) created a cluster file system based on multiple local AdvFS filesystems; testing carried out at Lawrence Livermore National Laboratory (LLNL) in 2000–2001 found that while the underlying AdvFS filesystem had adequate performance (albeit with high CPU utilisation), the PFS clustering layer on top of it performed poorly. On June 23, 2008, its source code was released by Hewlett-Packard under the GPL-2.0-only license (instead of the recently released GPLv3) at SourceForge in order to be compatible with the also GPL-2.0-only licensed Linux kernel. References External links Source code at Sourceforge.net Digital Equipment Corporation Disk file systems Formerly proprietary software