From: Ted Ts'o Subject: Re: Atomic non-durable file write API Date: Sun, 26 Dec 2010 20:04:34 -0500 Message-ID: <20101227010434.GG2595@thunk.org> References: <20101225031529.GA2595@thunk.org> <20101226221016.GF2595@thunk.org> <4D17DE0D.2070504@ontolinux.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel , linux-ext4@vger.kernel.org, Olaf van der Spek , Nick Piggin To: Christian Stroetmann Return-path: Content-Disposition: inline In-Reply-To: <4D17DE0D.2070504@ontolinux.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Mon, Dec 27, 2010 at 01:30:05AM +0100, Christian Stroetmann wrote: > An FS could easily have the rest of the functions of a database > management system (DBMS) as an FSDB, a hybrid if you wish. An > example for such a hybrid is the ext2/3-sqlite FS... What are you talking about? If you mean creating a sqlite database on top of an existing file system, sure that works fine. That's the right solution. But if you mean trying to access sqllite via a file-system interface (i.e., via FUSE), I suspect the result will be a disaster, precisely because the file system API isn't expressive enough to handle database functionality, and so the result ends up being a performance disaster. So the answer is "use a database, using a database API, if you have database requirements". > Furthermore, the performance of Oracle's solutions was and still is > so low, because they have a file system as a database that is > managed by a DBMS as a file that again is stored in an FS. Can you > see now what does the loss of performance? It was a disaster from a performance perspective even if the database was run on top of a raw block device.... > And Oracle fears FSs like R4 that have database(-like) > functionalities, so it took those technical features of R4 for the > BTRFS, which they thought could stop its show. > And also, Oracle has started some months ago again to promote its FS > in a DB in an FS concept. I've never heard of the R4 file system, and apparently Google hasn't either. But if you think BTRFS is a database, you're fooling yourself. There's a lot more to a database than just using a b-tree. > So, there must be something that is highly interesting with the idea > to use an FS as DBMS, not only for Oracle, but at least for the four > largest software companies. No, I think you're just utterly confused from a technical perspective. - Ted