Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758570Ab0G3MvS (ORCPT ); Fri, 30 Jul 2010 08:51:18 -0400 Received: from swm.pp.se ([212.247.200.143]:51097 "EHLO uplift.swm.pp.se" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756691Ab0G3MvR (ORCPT ); Fri, 30 Jul 2010 08:51:17 -0400 X-Greylist: delayed 629 seconds by postgrey-1.27 at vger.kernel.org; Fri, 30 Jul 2010 08:51:16 EDT Date: Fri, 30 Jul 2010 14:40:46 +0200 (CEST) From: Mikael Abrahamsson To: linux-kernel@vger.kernel.org Subject: Re: MD raid and different elevators (disk i/o schedulers) (fwd) Message-ID: User-Agent: Alpine 1.10 (DEB 962 2008-03-14) Organization: People's Front Against WWW MIME-Version: 1.0 Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1827 Lines: 43 Hi, this might be more appropriate for lkml (or is there another place?) because people with knowledge of how these layers interact might be here and not on linux-raid-ml ? If block cache is done on all levels and readahead is done on all levels, then quite a lot of redundant block information is going to exist in memory for all these layers? I can understand that it might make sense to keep block cache for the fs and perhaps for the drive layer, but md->dm(crypto)->lvm layers this might make less sense? What about default readahead for these devices? Doing readahead on dm device might be bad in some situations, perhaps good in others? ---------- Forwarded message ---------- Date: Thu, 29 Jul 2010 12:53:35 +0200 (CEST) From: Mikael Abrahamsson To: Fabio Muzzi Cc: linux-raid@vger.kernel.org Subject: Re: MD raid and different elevators (disk i/o schedulers) On Thu, 29 Jul 2010, Fabio Muzzi wrote: > Is this true? Are there compatibility issues using different i/o schedulers > with software raid? I'd actually like to raise this one level further: In the case of (drives)->md->dm(crypto)->lvm->fs, how do the schedulers, readahead settings, blocksizes, barriers etc interact thru all these layers? Is block caching done on all layers? Is readahead done on all layers? -- Mikael Abrahamsson email: swmike@swm.pp.se -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/