From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f182.google.com ([209.85.223.182]:33248 "EHLO mail-io0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752537AbcALMXO (ORCPT ); Tue, 12 Jan 2016 07:23:14 -0500 Received: by mail-io0-f182.google.com with SMTP id q21so381376140iod.0 for ; Tue, 12 Jan 2016 04:23:13 -0800 (PST) Subject: Re: [PATCH] BTRFS: Adds an option to select RAID Stripe size To: Christoph Anton Mitterer , Sanidhya Solanki References: <1451305451-31222-1-git-send-email-jpage.lkml@gmail.com> <1451341195.7094.0.camel@scientia.net> <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> <20160109221105.6b18fb8e@gmail.com> <1452527015.7801.1.camel@scientia.net> <20160111064956.573ec21b@gmail.com> <1452527868.7801.2.camel@scientia.net> Cc: Qu Wenruo , David Sterba , jbacik@fb.com, linux-btrfs@vger.kernel.org From: "Austin S. Hemmelgarn" Message-ID: <5694F025.1000800@gmail.com> Date: Tue, 12 Jan 2016 07:23:01 -0500 MIME-Version: 1.0 In-Reply-To: <1452527868.7801.2.camel@scientia.net> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 2016-01-11 10:57, Christoph Anton Mitterer wrote: > On Mon, 2016-01-11 at 06:49 -0500, Sanidhya Solanki wrote: >> I considered that, but, if you read the specification of modern HDDs >> carefully, it states that they are 4K or 512e sector size compatible, >> hence the concession. Also, older drive users may find this >> preferable. > But these are powers of 2,... why does one need 768, 3072, 6144, etc.? 768 I don't know, the other two though would provide proper stripe-alignment on a 8 or 14 disk hardware RAID6 setup using 512 byte sectors (that is, one stripe in BTRFS would span the full array). I personally think it should be restricted to multiples of 512, as that is the smallest sector size on any disk drive that is realistically usable with BTRFS. That would also provide 4k support, and beyond that 64k (which is where the really big drives are headed anyway), and also provide the ability to get proper stripe alignment on almost any hardware RAID configuration.