From: Matthias Bodenbinder <matthias@bodenbinder.de>
To: linux-btrfs@vger.kernel.org
Subject: Re: Question: raid1 behaviour on failure
Date: Thu, 21 Apr 2016 07:15:48 +0200 [thread overview]
Message-ID: <nf9nm4$204$1@ger.gmane.org> (raw)
In-Reply-To: <571784DF.3060800@oracle.com>
Am 20.04.2016 um 15:32 schrieb Anand Jain:
>> 1. mount the raid1 (2 disc with different size)
>
>> 2. unplug the biggest drive (hotplug)
>
> Btrfs won't know that you have plugged-out a disk.
> Though it experiences IO failures, it won't close the bdev.
Well, as far as I can tell mdadm can handle this use case. I tested that. I have an mdadm raid5 running. I accidentially unplugged a sata cable from one of the devices and the raid still worked. I did not even notice that the cable was unplugged until a few hours later. Then I plugged in the cable agaib and that was it. mdadm recovered the raid5 without any problem. -> This is redunancy!
>
>> 3. try to copy something to the degraded raid1
>
> This will work as long as you do _not_ run unmount/mount.
I did not umount the raid1 when I tried to copy something. As you can see from the sequence of events: I removed the drive and immdiately afterwards tried to copy something to the degraded array. This copy failed with a crash of the btrfs module. -> This is NOT redundancy.
The ummount and mount operations are coming afterwards.
In a nutshell I have to say that the btrfs behaviour is by no means compliant with my understanding of redundancy.
Matthias
next prev parent reply other threads:[~2016-04-21 5:15 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-18 5:06 Question: raid1 behaviour on failure Matthias Bodenbinder
2016-04-18 7:22 ` Qu Wenruo
2016-04-20 5:17 ` Matthias Bodenbinder
2016-04-20 7:25 ` Qu Wenruo
2016-04-21 5:22 ` Matthias Bodenbinder
2016-04-21 5:43 ` Qu Wenruo
2016-04-21 6:02 ` Liu Bo
2016-04-21 6:09 ` Qu Wenruo
2016-04-21 17:40 ` Matthias Bodenbinder
2016-04-22 6:02 ` Qu Wenruo
2016-04-23 7:07 ` Matthias Bodenbinder
2016-04-23 7:17 ` Matthias Bodenbinder
2016-04-26 8:17 ` Satoru Takeuchi
2016-04-26 15:16 ` Henk Slager
2016-04-20 13:32 ` Anand Jain
2016-04-21 5:15 ` Matthias Bodenbinder [this message]
2016-04-21 7:19 ` Anand Jain
2016-04-21 6:23 ` Satoru Takeuchi
2016-04-21 11:09 ` Austin S. Hemmelgarn
2016-04-21 11:28 ` Henk Slager
2016-04-21 17:27 ` Matthias Bodenbinder
2016-04-26 16:19 ` Henk Slager
2016-04-26 16:42 ` Holger Hoffstätte
2016-04-28 5:12 ` Matthias Bodenbinder
2016-04-28 5:24 ` Gareth Pye
2016-04-28 8:08 ` Duncan
2016-04-28 5:09 ` Matthias Bodenbinder
2016-04-28 19:14 ` Henk Slager
[not found] ` <57188534.1070408@jp.fujitsu.com>
2016-04-21 11:58 ` Qu Wenruo
2016-04-22 2:21 ` Satoru Takeuchi
2016-04-22 5:32 ` Qu Wenruo
2016-04-22 6:17 ` Satoru Takeuchi
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