From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-f193.google.com ([209.85.160.193]:40967 "EHLO mail-qt1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726736AbeK3A7J (ORCPT ); Thu, 29 Nov 2018 19:59:09 -0500 Received: by mail-qt1-f193.google.com with SMTP id d18so1977190qto.8 for ; Thu, 29 Nov 2018 05:53:42 -0800 (PST) Subject: Re: [PATCH] mkfs.xfs: don't go into multidisk mode if there is only one stripe References: <20181004175839.18736-1-idryomov@gmail.com> <24d229f3-1a75-a65d-5ad3-c8565cb32e76@sandeen.net> <20181004222952.GV31060@dastard> <67627995-714c-5c38-a796-32b503de7d13@sandeen.net> <20181005232710.GH12041@dastard> <20181006232037.GB18095@dastard> <36bc3f17-e7d1-ce8b-2088-36ff5d7b1e8b@sandeen.net> From: Ric Wheeler Message-ID: <0290ec9f-ab2b-7c1b-faaf-409d72f99e5f@gmail.com> Date: Thu, 29 Nov 2018 08:53:39 -0500 MIME-Version: 1.0 In-Reply-To: <36bc3f17-e7d1-ce8b-2088-36ff5d7b1e8b@sandeen.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Eric Sandeen , Dave Chinner , Ilya Dryomov Cc: xfs , Mark Nelson , Eric Sandeen , Mike Snitzer On 10/6/18 8:14 PM, Eric Sandeen wrote: > On 10/6/18 6:20 PM, Dave Chinner wrote: >>> Can you give an example of a use case that would be negatively affected >>> if this heuristic was switched from "sunit" to "sunit < swidth"? >> Any time you only know a single alignment characteristic of the >> underlying multi-disk storage. e.g. hardware RAID0/5/6 that sets >> iomin = ioopt, multi-level RAID constructs where only the largest >> alignment requirement is exposed, RAID1 devices exposing their chunk >> size, remote replication chunk alignment (because remote rep. is >> slow and so we need more concurrency to keep the pipeline full), >> etc. > So the tl;dr here is "given any iomin > 512, we should infer low seek > latency and parallelism and adjust geometry accordingly?" > > -Eric Chiming in late here, but I do think that every decade or two (no disrespect to xfs!), it is worth having a second look at how the storage has changed under us. The workload that has lots of file systems pounding on a shared device for example is one way to lay out container storage. No argument about documenting how to fix this with command line tweaks for now, but maybe this would be a good topic for the next LSF/MM shared track of file & storage people to debate? Ric