From: "Darrick J. Wong" Subject: Re: Some thoughts about providing data block checksumming for ext4 Date: Wed, 26 Nov 2014 15:47:06 -0800 Message-ID: <20141126234706.GN10043@birch.djwong.org> References: <20141103233308.GA27842@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org, dm-devel@redhat.com To: "Theodore Ts'o" Return-path: Received: from aserp1040.oracle.com ([141.146.126.69]:21663 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752760AbaKZXrO (ORCPT ); Wed, 26 Nov 2014 18:47:14 -0500 Content-Disposition: inline In-Reply-To: <20141103233308.GA27842@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: Sigh... Well, I wrote up a preliminary version of dm-checksum and then realized that I've pretty much just built a crappier version of dm-dedupe, but without the dedupe part. Given that it stores checksums in a btree which claims to be robust through failures and gives us automatic deduplication, I wonder if it we could achieve our aims by modifying dm-dedupe to verify the checksums on the read path? I guess it would be interesting to see how bad the performance hit is with the online dedupe part enabled or disabled. dm-dedupe v2 went out on the mailing list last August, which I missed. :( Unless... there's a specific reason nobody mentioned dm-dedupe here? --D