From mboxrd@z Thu Jan 1 00:00:00 1970 From: Artur Paszkiewicz Subject: Re: [PATCH 0/2] md: Add support for Multiple PPLs Date: Mon, 28 Aug 2017 09:44:20 +0200 Message-ID: <110e9aa4-4215-7f29-dd05-7d00dde6da9b@intel.com> References: <20170816151346.23382-1-pawel.baldysiak@intel.com> <20170817180331.baxoqhgbqi5q6fvx@kernel.org> <4e72946d-3bdc-8a69-0b44-591570aae3a2@intel.com> <20170821161426.of5z62r45unlh2en@kernel.org> <20170825215300.xgkdklgi4lxvhxrx@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170825215300.xgkdklgi4lxvhxrx@kernel.org> Content-Language: en-US Sender: linux-raid-owner@vger.kernel.org To: Shaohua Li , Pawel Baldysiak Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 08/25/2017 11:53 PM, Shaohua Li wrote: > On Fri, Aug 25, 2017 at 10:02:07PM +0200, Pawel Baldysiak wrote: >> On 08/21/2017 06:14 PM, Shaohua Li wrote> Can you elaborate more? >>> >> Storage presented to the host may have a RAID on the back-end. For NVMe >> SSDs, the 1.3 specification provided a field to advertise chunk >> boundaries: Identify Namespace NOIOB. We need to span the entire stripe >> to utilize the total available capacity, otherwise we'll repeatedly >> write to only a subset, increasing write amplification factor. The new >> PPL approach is designed to access the full capacity. > > Ok, this makes sense. The 1MB area looks arbitrary though. What if the > chunk is 2MB? Could we make it configurable? Actually, it is configurable by 'ppl_size' which comes from mdadm. The 1MB is what the current RSTe standard defines but it will be possible to change it without affecting the kernel. Thanks, Artur