From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shaohua Li Subject: Re: Shouldn't the /sys/block/md*/queue/max_*sectors_kb be set to the chunk size? Date: Thu, 18 May 2017 11:50:23 -0700 Message-ID: <20170518185023.3z5byy5uqpfb46w6@kernel.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Chris Worley Cc: linuxraid List-Id: linux-raid.ids On Thu, May 18, 2017 at 05:52:28AM -1000, Chris Worley wrote: > I'm obviously missing something... > > If chunk size is a stride, why is the > /sys/block/md*/queue/max_*sectors_kb being inherited from one of the > underlying devices rather than being set to the chunk size or the > drive multiple of their max sector settings? We set it to chunk size unless underlying disks have a smaller max_*sectors_kb. Underlying disks usually have much bigger max_sectors than chunk size. > Or, in other words, would the chunk size setting have a natural upper > bound/limit of one of the drives max_sectors, or the sum of all of the > constituent drives max sectors? I don't know such upper bound and don't think it matters. The max_sectors basically is the size we split the bio to fit for one underlying disk. Thanks, Shaohua