From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shaohua Li Subject: Re: [PATCH v5 0/7] Partial Parity Log for MD RAID 5 Date: Thu, 9 Mar 2017 15:32:40 -0800 Message-ID: <20170309233240.r64itd7oreuxkumz@kernel.org> References: <20170309090003.13298-1-artur.paszkiewicz@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170309090003.13298-1-artur.paszkiewicz@intel.com> Sender: linux-raid-owner@vger.kernel.org To: Artur Paszkiewicz Cc: shli@fb.com, linux-raid@vger.kernel.org List-Id: linux-raid.ids On Thu, Mar 09, 2017 at 09:59:56AM +0100, Artur Paszkiewicz wrote: > This series of patches implements the Partial Parity Log for RAID5 arrays. The > purpose of this feature is closing the RAID 5 Write Hole. It is a solution > alternative to the existing raid5-cache, but the logging workflow and much of > the implementation is based on it. > > The main differences compared to raid5-cache is that PPL is a distributed log - > it is stored on array member drives in the metadata area and does not require a > dedicated journaling drive. Write performance is reduced by up to 30%-40% but > it scales with the number of drives in the array and the journaling drive does > not become a bottleneck or a single point of failure. PPL does not protect from > losing in-flight data, only from silent data corruption. More details about how > the log works can be found in patches 3 and 5. > > This feature originated from Intel RSTe, which uses IMSM metadata. PPL for IMSM > is going to be included in RSTe implementations starting with upcoming Xeon > platforms and Intel will continue supporting and maintaining it. This patchset > implements PPL for external metadata (specifically IMSM) as well as native MD > v1.x metadata. > > Changes in mdadm are also required to make this fully usable. Patches for mdadm > will be sent later. Looks good, I'll apply this series into next. There are some small issues I replied separately. Please send a separate patch to fix them if they make sense, I'll integrate them locally. Thanks, Shaohua