From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailgw-02.dd24.net ([193.46.215.43]:38854 "EHLO mailgw-02.dd24.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751815AbcAESsX (ORCPT ); Tue, 5 Jan 2016 13:48:23 -0500 Message-ID: <1452019697.5722.10.camel@scientia.net> Subject: Re: [PATCH] BTRFS: Adds an option to select RAID Stripe size From: Christoph Anton Mitterer To: dsterba@suse.cz Cc: linux-btrfs@vger.kernel.org Date: Tue, 05 Jan 2016 19:48:17 +0100 In-Reply-To: <20160105104455.GS4227@twin.jikos.cz> References: <20151228153801.6561feff@gmail.com> <1451352069.7094.3.camel@scientia.net> <20151228164333.2b8d8336@gmail.com> <1451360528.7094.7.camel@scientia.net> <20151228190336.59a3f440@gmail.com> <1451363188.7094.23.camel@scientia.net> <20151229180643.GD4227@twin.jikos.cz> <20160102065207.4eec760a@gmail.com> <56887B40.10105@gmx.com> <1451787985.6645.12.camel@scientia.net> <20160105104455.GS4227@twin.jikos.cz> Content-Type: multipart/signed; micalg="sha-512"; protocol="application/x-pkcs7-signature"; boundary="=-Kx2v1mNHltaHowAS8Jo5" Mime-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org List-ID: --=-Kx2v1mNHltaHowAS8Jo5 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2016-01-05 at 11:44 +0100, David Sterba wrote: > We have a full 32 bit number space, so multiples of power of 2 are > also > possible if that makes sense. Hmm that would make a maximum of 4GiB RAID chunks... perhaps we should reserve some of the higher bits for a multiplier, in case 4GiB would ever become too little O;-) > In general we don't need to set additional > limitations besides minimum, maximum and "minimal step". And that can/should be done in the userland. > > Are there any concerns/constraints with too small/too big chunks > > when > > these play together with lower block layers (I'd guess not). >=20 > I don't think so. Well I was mainly thinking about dm-crypt, that uses 512B blocks and in fact that size wouldn't be easy to change, as (IIRC) larger block sizes make XTS less secure. Obviously *this* isn't anything that btrfs would have to worry about, especially as we're anyway on a higher block layer level,.. but it just reminded me that there can be cases where too large / too small may actually cause issues. 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