Date: Wed, 7 Feb 2001 21:48:05 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: sam@errno.com (Sam Leffler) Cc: zzhang@cs.binghamton.edu (Zhiui Zhang), freebsd-fs@FreeBSD.ORG Subject: Re: Design a journalled file system Message-ID: <200102072148.OAA25001@usr08.primenet.com> In-Reply-To: <0e9101c09086$5ca812b0$24a6d4d1@melange> from "Sam Leffler" at Feb 06, 2001 01:47:11 PM
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> If you really want to work on another filesystem, learn about/from SGI's > XFS. They've made a GPL'd version for Linux version available for public > ftp. Unfortunately, this license means that it can not be distributed compiled into a FreeBSD kernel, since clause 6 of the GPL will specifically prohibit such distribution. The upshot of this is that it can never be the default FS used to boot FreeBSD, out of the box, nor to install by default, since the module would have to be loaded from an FS which the system can not understand until after it has loaded the module. Historically, the soloution that is often suggested for this second problem is to use a simpler boot FS that the kernel understands (Xenix, SCO UNIX, and SVR4 have all taken this approach), but doing this renders the bootfs to be a single point of failure for boot, and therefore the increased MTBF that supposedly comes from using an advanced FS does nothing for the overall MTBF. In other words, the SGI XFS is an interesting curiousity, and may or may not be a useful reference implementation for another work, but it can never be used in a commercially usable OS, for which source code is inconvenient or impossible to distribute (even SGI can not take modifications made to repair bugs in the Linux version, without having to place all of IRIX under the GPL -- this they can not do, since IRIX contains code that was licensed from vendors who are not anxious to have their property given away free). I rather suspect that the GPL was intentionally chosen by SGI to permit them to jump on the Linux/Open Source bandwagon, without exposing them to the risk of a commercial organization which competes with SGI being able to benefit from the technology being released; QNX, Windows NT, and Solaris are all obvious candidates for this anticompetitive practice). Conclusion: Creating a truly free journalled FS implementation, even if it were to end up being bidirectionally data-compatible with XFS disks, is a worthy project. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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