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Subject: Re: gmirror and a flaky member
To: Andriy Gapon <avg@FreeBSD.org>, freebsd-geom@FreeBSD.org
References: <7e4164bd-9804-02d5-5990-bc15354989e9@FreeBSD.org>
 <77c40117-35ab-2430-07f8-e1df6b87fe1c@FreeBSD.org>
From: Miroslav Lachman <000.fbsd@quip.cz>
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Date: Fri, 6 Jan 2017 16:09:33 +0100
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Andriy Gapon wrote on 2017/01/06 11:12:
> On 06/01/2017 11:54, Andriy Gapon wrote:
>>
>> Can a geom mirror handle a member that gets disconnected and then reappears again?
>>
>> What I am seeing right now is that the mirror does not pick up the member when
>> it reappears.   I have to add it back manually.

It is intentional to mark disappeared device as broken.
If you want to remove working device from gmirror, you must use gmirror 
remove command (or gmirror deactivate).

> To add more substance, here is what gets logged when the disk disappears:
>
> GEOM_MIRROR: Request failed (error=6). ada0p2[READ(offset=2517700608, length=4096)]
> GEOM_MIRROR: Device swap: provider ada0p2 disconnected.
>
> And here's what gets logged when the disk reappears:
> GEOM_MIRROR: Component ada0p2 (device swap) broken, skipping.
> GEOM_MIRROR: Cannot add disk ada0p2 to swap (error=22).

Was the disk removed by user or was it by some bad event?

>> Even worse, the commands I have
>> to execute are:
>> $ gmirror forget ...
>> $ gmirror insert ...
>>
>> This does not appear to be a graceful way of reactivating the member.

You can re-activate only member which was correctly deactivated. Not one 
yanked out without any "graceful" command.

And as gmirror doesn't work as ZFS mirror (cannot do resilver) the 
re-added device is always fully rebuilt.

Miroslav Lachman