From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Mason Subject: Re: [RFC] proposal for a btrfs filesystem layout Date: Mon, 23 Nov 2009 20:26:08 -0500 Message-ID: <20091124012608.GF24068@think> References: <200911201950.06662.kreijack@libero.it> <934f64a20911201124q2a42fddek87d3f8fe864b3c41@mail.gmail.com> <20091120195017.GZ3110@think> <934f64a20911201205j70b5b9cfm40260a4a3a6c7b0b@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Cc: linux-btrfs@vger.kernel.org To: David Nicol Return-path: In-Reply-To: <934f64a20911201205j70b5b9cfm40260a4a3a6c7b0b@mail.gmail.com> List-ID: On Fri, Nov 20, 2009 at 02:05:11PM -0600, David Nicol wrote: > On Fri, Nov 20, 2009 at 1:50 PM, Chris Mason = wrote: > > COW semantics require touching btree nodes all the way up to the ro= ot of > > the btree, but this is different from the directory. =A0Directories= are > > stored in the btree, but you won't have to touch more than 8 or so = btree > > levels regardless of how deep your directory tree is. > > > > -chris >=20 > Thanks for straightening me out on that point. >=20 > Still, 8 might be a lot. >=20 > Regardless of the decoupling of btrees and directories, am I right in > thinking that mounted subvolumes instead of directories would (1) > reduce contention It might, it depends on the workload. But yes, one point of big contention is the root node of the btree and each subvolume has its own root. > (2) reduce the number of levels touched since number > of levels is a function of the number of fs entities in the volume, > therefore It depends on the overall btree size. Probably. > (3) defining a file system entity that transparently becomes > a mounted subvolume (by transparently I mean without an additional > mount command) and (4) crafting a utility to streamline > creation-and-implied-mounting of the entity type from #3 would make > sense? Sure. It definitely makes sense to explore the subvolume and snapshotting user interfaces. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" = in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html