Date: Wed, 23 Apr 2003 21:29:17 +0000 From: Nuno Teixeira <nunotex@m-net.arbornet.org> To: "Jeroen C. van Gelderen" <jeroen@vangelderen.org> Cc: current@freebsd.org Subject: Re: Little UFS2 FAQ Message-ID: <20030423212917.GB2675@gw.tex.bogus> In-Reply-To: <64FEF4DA-758E-11D7-9A25-000393754B1C@vangelderen.org> References: <64FEF4DA-758E-11D7-9A25-000393754B1C@vangelderen.org>
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Hi, Great work on this FAQ. For some time that I'm looking for a faq like this. I searching for such a FAQ related to SCHED_4BSD and SCHED_ULE schedulers for people who just understand funcionality. It is possible to create a faq about this subject? Thanks very much, Nuno Teixeira On Wed, Apr 23, 2003 at 03:20:47PM +0200, Jeroen C. van Gelderen wrote: > Little UFS2 FAQ (20023/04/23), culled from contributions by: > > Peter Schultz <peter@jocose.org> > "Poul-Henning Kamp" <phk@phk.freebsd.dk> > Marcin Dalecki <mdcki@gmx.net> > CARTER Anthony <a.carter@cordis.lu> > Robert Watson <rwatson@freebsd.org> > Terry Lambert <tlambert2@mindspring.com> > Frank van der Linden <fvdl@wasabisystems.com> > Manfred Antar <null@pozo.com> > Narvi <narvi@haldjas.folklore.ee> > Takahashi Yoshihiro <nyan@jp.FreeBSD.org> > Alexander Pohoyda <alexander.pohoyda@gmx.net> > Bruce Evans <bde@zeta.org.au> > "Wilkinson,Alex" <Alex.Wilkinson@dsto.defence.gov.au> > > > > What is UFS1? > > The long-time BSD(?) native filesystem. > > > > What is UFS2? > > UFS2 is an extension to the well-known UFS. It adds 64 bit block > pointers (breaking the 1T barrier), support for extended file storage, > and a few other things. > > Short summary of changes: > o 64-bit pointers up the wazoo > (implies that inodes have doubled in size, and now are 256 bytes) > o Layout and functional changes to help support variable-size blocks > (extent-like allocation) > o Extension of various flag fields > o Addition of per-inode extended attribute extent > o Lazy inode initialization (watch newfs(8) fly) > > Apart from these modifications all UFS1 code is being used in UFS2 > unchanged. > > > > What is the difference between UFS and FFS? > > UFS (and UFS2) define on-disk data layout. FFS sits on top of UFS (1 or > 2) and provides directory structure information, etc, etc. This FAQ is > about a revision of UFS named UFS2. > > > > What is the rationale for UFS2? > > The motivating factor in the layout change was the need for better > Extended Attribute (EA) support, and while the developers were at it > they figured they'd do a bunch of other useful things too. UFS2 uses > the same basic technologies as modern UFS1 (inodes, linear directory > layout, soft updates, snapshotting, background file system checking, > etc) so it was a relatively low-risk change. > > > > Why did you not add <feature> while you were at it? > > It would most likely require significant changes whereas the developers > wanted to restrict themselves to low-risk modifications only. See > previous question. > > > > Which OSes support UFS2? > > FreeBSD and NetBSD. (Others?) > > > > What is the UFS2 status on FreeBSD? > > As of 2003/04/20, newfs(8) and sysinstall(8) will create UFS2 file > systems by default, unless explicitly specified. Users wanting to > create UFS1 file systems for whatever reason (interoperability with > earlier versions, etc) should be sure to employ the -O1 flag to > newfs(8), or hit '1' in the label editor in sysinstall(8) to select > UFS1. > > > > What is the UFS2 status on NetBSD? > > As of 2003/04/02 UFS2 is not (yet) the default type for FFS > filesystems. newfs(8) will create a normal FFS filesystem by default. > If you want an UFS2 fileystem, specify "-O 2" as an option. > > No additional kernel options are needed for UFS2 support, it's > contained within the FFS code. > > Please note that older fsck binaries will complain a bit about > filesystems if you boot a new kernel, because of some superblock > changes. This is harmless. However, if you have 1.6 fsck binaries, they > will signal a fatal superblock mismatch with the first alternate, > because they compare too many fields (even ones that aren't useful). > This is annoying, and I'd advise peole to upgrade their fsck_ffs binary > before using a new kernel. 1.6.1 will have an fsck that is forward > compatible. Again, none of this signals actual filesystem damage, but > it's still annoying. > > > > Does the /boot/loader now understand UFS2 on the root filesystem (i386)? > > Yes, modulo the restriction that your root filesystem cannot be larger > than 1.5TB. David Schultz et al. proposed a patch to remove this > limitation. > > > > Does the /boot/loader now understand UFS2 on the root filesystem (PC98)? > > Nope. It is unknown if work is underway to address this. > > > > Is there a UFS to UFS2 conversion tool? > > No. You can however dump/restore from UFS to UFS2. > > > > Will "dump" on UFS and "restore" on UFS2 filesystem work? > > Yes, that will work. > > > > Does UFS2 dynamically allocate inodes? > > No it does not. Inodes are preallocated, but UFS2 lazily initializes > them. This mainly means that newfs(8) runs much faster. > > > > Does Grub work with UFS2? > > No. Not yet(?). > > > -- > Jeroen C. van Gelderen - jeroen@vangelderen.org > > "They accused us of suppressing freedom of expression. > This was a lie and we could not let them publish it." > -- Nelba Blandon, > Nicaraguan Interior Ministry Director of Censorship > > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" -- /* PGP fingerprint: C6D1 06ED EB54 A99C 6B14 6732 0A5D 810D 727D F6C6 */
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