From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andras Korn Subject: Re: RAID10: how much does chunk size matter? Can partial chunks be written? Date: Sat, 5 Jan 2013 08:44:07 +0100 Message-ID: <20130105074406.GB16375@hellgate> References: <20130104175458.GA3298@hellgate> <50E75CE2.8060105@hardwarefreak.com> <20130104234113.GA14799@hellgate> <50E777DC.1060804@hardwarefreak.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <50E777DC.1060804@hardwarefreak.com> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Fri, Jan 04, 2013 at 06:46:20PM -0600, Stan Hoeppner wrote: > >> 1. What filesystem are you using? > > > > The filesystem is the "application": it's zfsonlinux. I'm putting it on > > RAID10 instead of using the disks natively because I want to encrypt it > > using LUKS, and encrypting each disk separately seemed wasteful of CPU (I > > only have 3 cores). > > I just love when the other shoe drops and it turns out to be a size 13 > boot... filled with lead. > > Any reason why you intentionally omitted these critical details from > your initial post? Yes: I thought I was asking a theoretical question, not for advice on tuning my specific setup, and thought - apparently correctly, I might add :) - that including these details would only get everyone sidetracked into trying to optimise for a specific application. I don't have a specific application with a specific access pattern because I have to run all sorts of applications on this box, on top of this array, simultaneously. But meanwhile I think I have received an answer: the fact that zfs uses blocks of 128k or less does not automatically mean that write performance would suffer on a 512k-chunk RAID10 array because the Linux RAID10 implementation, very sensibly, doesn't insist on writes being aligned to chunk boundaries. So thanks. -- Andras Korn Reality is merely an illusion, albeit a very persistent one.