From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Guilherme G. Piccoli" Subject: Re: [PATCH 1/2] md/raid0: Introduce new array state 'broken' for raid0 Date: Tue, 30 Jul 2019 09:18:54 -0300 Message-ID: <000c20fe-3bcd-2dff-a5ab-9a294bdc7746@canonical.com> References: <20190729203135.12934-1-gpiccoli@canonical.com> <20190729203135.12934-2-gpiccoli@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Bob Liu , linux-raid@vger.kernel.org Cc: linux-block@vger.kernel.org, jay.vosburgh@canonical.com, dm-devel@redhat.com, songliubraving@fb.com, neilb@suse.com List-Id: linux-raid.ids On 30/07/2019 03:20, Bob Liu wrote: > [...] >> + * broken >> + * RAID0-only: same as clean, but array is missing a member. >> + * It's useful because RAID0 mounted-arrays aren't stopped >> + * when a member is gone, so this state will at least alert >> + * the user that something is wrong. > > > Curious why only raid0 has this issue? > > Thanks, -Bob Hi Bob, I understand that all other levels have fault-tolerance logic, while raid0 is just a "bypass" driver that selects the correct underlying device to send the BIO and blindly sends it. It's known to be a performance-only /lightweight solution whereas the other levels aim to be reliable. I've quickly tested raid5 and rai10, and see messages like this on kernel log when removing a device (in raid5): [35.764975] md/raid:md0: Disk failure on nvme1n1, disabling device. md/raid:md0: Operation continuing on 1 devices. The message seen in raid10 is basically the same. As a (cheap) comparison of the complexity among levels, look that: <...>/linux-mainline/drivers/md# cat raid5* | wc -l 14191 <...>/linux-mainline/drivers/md# cat raid10* | wc -l 5135 <...>/linux-mainline/drivers/md# cat raid0* | wc -l 820 Cheers, Guilherme