From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Mackall Subject: Re: [RFC] TileFS - a proposal for scalable integrity checking Date: Mon, 30 Apr 2007 12:59:26 -0500 Message-ID: <20070430175926.GU11115@waste.org> References: <20070428220522.GN11166@waste.org> <20070429232349.GA19937@thunk.org> <20070430014042.GL11115@waste.org> <20070430172624.GB19149@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org To: Theodore Tso Return-path: Received: from waste.org ([66.93.16.53]:52978 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1946547AbXD3R7e (ORCPT ); Mon, 30 Apr 2007 13:59:34 -0400 Content-Disposition: inline In-Reply-To: <20070430172624.GB19149@thunk.org> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Mon, Apr 30, 2007 at 01:26:24PM -0400, Theodore Tso wrote: > On Sun, Apr 29, 2007 at 08:40:42PM -0500, Matt Mackall wrote: > > chunkfs. The other is reverse maps (aka back pointers) for blocks -> > > inodes and inodes -> directories that obviate the need to have large > > amounts of memory to check for collisions. > > Yes, I missed the fact that you had back pointers for blocks as well > as inodes. So the block table in the tile header gets used for > determing if a block is free, much like is done with FAT, right? We could eliminate the block bitmap, but I don't think there's much reason to. It improves allocator performance with negligible footprint and improves redundancy. > That's a clever system; I like it. It does mean that there is a lot > more metadata updates, but since you're not journaling, that should > counter that effect to some extent. I had actually envisioned this as working with or without a journal. I suspect there are ways to keep the performance downside here low. > IMHO, it's definitely worth a try to see how well it works! I'm not much of an FS hacker and I've got a lot of other projects in the air, but I may give it a shot. Any help on this front would be appreciated. -- Mathematics is the supreme nostalgia of our time.