From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Mamedov Subject: Re: [PATCH] md/raid0: Fail BIOs if their underlying block device is gone Date: Tue, 30 Jul 2019 01:36:55 +0500 Message-ID: <20190730013655.229020ea@natsu> References: <20190729193359.11040-1-gpiccoli@canonical.com> <20190730011850.2f19e140@natsu> <053c88e1-06ec-0db1-de8f-68f63a3a1305@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <053c88e1-06ec-0db1-de8f-68f63a3a1305@canonical.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: "Guilherme G. Piccoli" Cc: linux-block@vger.kernel.org, Song Liu , NeilBrown , linux-raid@vger.kernel.org, dm-devel@redhat.com, jay.vosburgh@canonical.com List-Id: dm-devel.ids On Mon, 29 Jul 2019 17:27:15 -0300 "Guilherme G. Piccoli" wrote: > Hi Roman, I don't think this is usual setup. I understand that there are > RAID10 (also known as RAID 0+1) in which we can have like 4 devices, and > they pair in 2 sets of two disks using stripping, then these sets are > paired using mirroring. This is handled by raid10 driver however, so it > won't suffer for this issue. > > I don't think it's common or even makes sense to back a raid1 with 2 > pure raid0 devices. It might be not a usual setup, but it is a nice possibility that you get with MD. If for the moment you don't have drives of the needed size, but have smaller drives. E.g.: - had a 2x1TB RAID1; - one disk fails; - no 1TB disks at hand; - but lots of 500GB disks; - let's make a 2x500GB RAID0 and have that stand in for the missing 1TB member for the time being; Or here's for a detailed rationale of a more permanent scenario: https://louwrentius.com/building-a-raid-6-array-of-mixed-drives.html -- With respect, Roman From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 92727C433FF for ; Mon, 29 Jul 2019 20:36:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6A09020693 for ; Mon, 29 Jul 2019 20:36:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728400AbfG2Ug6 (ORCPT ); Mon, 29 Jul 2019 16:36:58 -0400 Received: from len.romanrm.net ([91.121.75.85]:44078 "EHLO len.romanrm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727985AbfG2Ug6 (ORCPT ); Mon, 29 Jul 2019 16:36:58 -0400 Received: from natsu (unknown [IPv6:fd39::e99e:8f1b:cfc9:ccb8]) by len.romanrm.net (Postfix) with SMTP id 04387202D3; Mon, 29 Jul 2019 20:36:55 +0000 (UTC) Date: Tue, 30 Jul 2019 01:36:55 +0500 From: Roman Mamedov To: "Guilherme G. Piccoli" Cc: linux-raid@vger.kernel.org, linux-block@vger.kernel.org, dm-devel@redhat.com, jay.vosburgh@canonical.com, NeilBrown , Song Liu Subject: Re: [PATCH] md/raid0: Fail BIOs if their underlying block device is gone Message-ID: <20190730013655.229020ea@natsu> In-Reply-To: <053c88e1-06ec-0db1-de8f-68f63a3a1305@canonical.com> References: <20190729193359.11040-1-gpiccoli@canonical.com> <20190730011850.2f19e140@natsu> <053c88e1-06ec-0db1-de8f-68f63a3a1305@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, 29 Jul 2019 17:27:15 -0300 "Guilherme G. Piccoli" wrote: > Hi Roman, I don't think this is usual setup. I understand that there are > RAID10 (also known as RAID 0+1) in which we can have like 4 devices, and > they pair in 2 sets of two disks using stripping, then these sets are > paired using mirroring. This is handled by raid10 driver however, so it > won't suffer for this issue. > > I don't think it's common or even makes sense to back a raid1 with 2 > pure raid0 devices. It might be not a usual setup, but it is a nice possibility that you get with MD. If for the moment you don't have drives of the needed size, but have smaller drives. E.g.: - had a 2x1TB RAID1; - one disk fails; - no 1TB disks at hand; - but lots of 500GB disks; - let's make a 2x500GB RAID0 and have that stand in for the missing 1TB member for the time being; Or here's for a detailed rationale of a more permanent scenario: https://louwrentius.com/building-a-raid-6-array-of-mixed-drives.html -- With respect, Roman