From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keith Busch Subject: Re: [PATCH v2 2/2] dm unstripe: Add documentation for unstripe target Date: Tue, 12 Dec 2017 07:45:56 -0700 Message-ID: <20171212144556.GF11218@localhost.localdomain> References: <20171211160019.20518-1-scott.bauer@intel.com> <20171211160019.20518-3-scott.bauer@intel.com> <00fdc58c-d8e9-6b42-727d-ab70d5ce1b0a@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <00fdc58c-d8e9-6b42-727d-ab70d5ce1b0a@gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: Nikolay Borisov Cc: Scott Bauer , dm-devel@redhat.com, snitzer@redhat.com, agk@redhat.com, linux-kernel@vger.kernel.org, jonathan.derrick@intel.com List-Id: dm-devel.ids On Tue, Dec 12, 2017 at 01:35:13PM +0200, Nikolay Borisov wrote: > On 11.12.2017 18:00, Scott Bauer wrote: > > + As an example: > > + > > + Intel NVMe drives contain two cores on the physical device. > > + Each core of the drive has segregated access to its LBA range. > > + The current LBA model has a RAID 0 128k stripe across the two cores: > > + > > + Core 0: Core 1: > > + __________ __________ > > + | LBA 511| | LBA 768| > > + | LBA 0 | | LBA 256| > > + ⎻⎻⎻⎻⎻⎻⎻⎻⎻⎻ ⎻⎻⎻⎻⎻⎻⎻⎻⎻⎻ > > If it's 128k stripe shouldn't it be LBAs 0/256 on core0 and LBAs 128/511 > on core1? Ah, this device's makers call the "stripe" size what should be called "chunk". This device has a 128k chunk per core with two cores, so the full stripe is 256k. The above should have core 0 owning LBA 512 rather than 511 (assuming 512b LBA format).