From: Andreas Dilger Subject: Re: breaking ext4 to test recovery Date: Sat, 2 Apr 2011 08:50:38 -1000 Message-ID: References: <25B374CC0D9DFB4698BB331F82CD0CF20D61B8@wdscexbe08.sc.wdc.com> <4D91E39A.3000800@redhat.com> <6617927D-7C9C-4D02-97FD-C9CC75609448@dilger.ca> <4D9503C0.8080804@redhat.com> <06ABAED6-3569-4A30-816B-6A7A53A652D1@dilger.ca> <4D9718BB.2070005@gmail.com> Mime-Version: 1.0 (iPhone Mail 8F190) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Cc: Eric Sandeen , Daniel Taylor , "linux-ext4@vger.kernel.org development" , Johann Lombardi To: Ric Wheeler Return-path: Received: from mail-pw0-f46.google.com ([209.85.160.46]:51980 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757066Ab1DCAqz convert rfc822-to-8bit (ORCPT ); Sat, 2 Apr 2011 20:46:55 -0400 Received: by pwi15 with SMTP id 15so974323pwi.19 for ; Sat, 02 Apr 2011 17:46:54 -0700 (PDT) In-Reply-To: <4D9718BB.2070005@gmail.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 2011-04-02, at 2:38 AM, Ric Wheeler wrote: > The device mapper developers are looking at having a device mapper target that can be used as a hot block cache - say given a S-ATA disk and a PCI-e SSD, you would store the hot blocks on the PCI-e card. There was a patch posted around December called bcache which did this same thing. I don't recall if it was a DM target or not. > What might be a great simulation would be to have a way to destroy that cache, assuming we could get a cache policy that simulates some reasonable, disk like caching policy :) The one difficulty with DM targets is that they cannot be used with non DM devices. That was one of the advantages of EVMS (if anyone remembers that) - it could work with any existing block device. Cheers, Andreas