Date: Fri, 21 Sep 2007 14:45:35 +0200 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-fs@freebsd.org Subject: Re: Writing contigiously to UFS2? Message-ID: <fd0edf$7jd$1@sea.gmane.org> In-Reply-To: <46F3B520.1070708@FreeBSD.org> References: <46F3A64C.4090507@fluffles.net> <fd0aaj$poh$1@sea.gmane.org> <46F3B520.1070708@FreeBSD.org>
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[-- Attachment #1 --] Stefan Esser wrote: > Ivan Voras wrote: >> (ZFS is not the ultimate solution: 1) replacing UFS monoculture with ZFS >> monoculture will sooner or later yield problems, and 2) sometimes a >> "dumb" unix filesystem is preferred to the "smart" ZFS). > > Both XFS and ReiserFS are quite complex compared to UFS definitely > not well described by the term "dumb" ;-) Of course, I mean no disrespect to them, I've read enough papers on them to realize their complexity :) By "dumb" I meant they behave like "point them to a device and they will stick to it", i.e. they don't come with a volume manager. > The FFS paper by McKusick et.al describes the historical allocation > strategy, which was somewhat modified in FreeBSD a few years ago in > order to adapt to modern disk sizes (larger cylinder groups, meaning > it is not a good idea to create each new directory in a new cylinder > group). [thinking out loud:] From experience (not from reading code or the docs) I conclude that cylinder groups cannot be larger than around 190 MB. I know this from numerous runnings of newfs and during development of gvirstor which interacts with cg in an "interesting" way. I know the reasons why cgs exist (mainly to lower latencies from seeking) but with todays drives and memory configurations it would sometimes be nice to make them larger or in the extreme, make just one cg that covers the entire drive. Though, this extreme would in case of concat configurations put all of block and inode metadata on the first drive which could have interesting effects on performance. Of course, with seek-less drives (solid state) there's no reason to have cgs at all. [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iD8DBQFG87zvldnAQVacBcgRA+QDAJ9DAe3v2ddR9WZRzx/KlKjBye0erACfYHMg VoW1ozr75Mbml3V8oN0Sw3M= =DEqb -----END PGP SIGNATURE-----help
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