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From: "John Stoffel" <john@stoffel.org>
To: Zdenek Kabelac <zkabelac@redhat.com>
Cc: dm-devel@redhat.com, Drew Hastings <dhastings@crucialwebhost.com>
Subject: Re: Possible bug in mirror target
Date: Sun, 10 Feb 2019 16:58:06 -0500	[thread overview]
Message-ID: <23648.40558.660430.523285@quad.stoffel.home> (raw)
In-Reply-To: <27e658d7-265f-b765-1b19-d61f52da8457@redhat.com>

>>>>> "Zdenek" == Zdenek Kabelac <zkabelac@redhat.com> writes:

Zdenek> Dne 05. 02. 19 v 1:47 Drew Hastings napsal(a):
>> Hi,
>> 
>> I'm assuming all user space code is expected to use the handle_errors feature, 
>> so this isn't that big of a deal. I'm also using 4.19.13, which I think is 
>> more recent than the latest update to dm-raid1.c
>> 
>> That said, there may be a bug that causes the entire mirror to crash if there 
>> is an error on the first leg of the mirror, but not on the 2nd leg.
>> 
>> Works fine if you do cause IO errors on the 2nd leg:
>> 
>> root@kernel-dev:~# dmsetup create zerodev --table "0 1073741824 zero"
>> root@kernel-dev:~# dmsetup create errordev --table "0 1073741824 error"
>> 
>> 
>> root@kernel-dev:~# dmsetup create mirror-table --table "0 1073741824 mirror 
>> core 2 524288 nosync 2 /dev/mapper/zerodev 0 /dev/mapper/errordev 0 0"

Zdenek> There are 2 operational modes for old dm mirror target.
Zdenek> One requires to handle errors externally. Please check i.e. the following 
Zdenek> guide for mirror target:

Zdenek> https://wiki.gentoo.org/wiki/Device-mapper

Zdenek> Lvm2 is using 'dmeventd' to service this error handling
Zdenek> (i.e. dropping the mirror leg or allocating replacement one).

Is it time to remove the dm-mirror target then?  Or to deprecate it?
Or to just silently replace it with something that does the right
thing when errors happen?  I can't think of why *anyone* would want to
use the dm-mirror target as it now seems to work.

John

  reply	other threads:[~2019-02-10 21:58 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-05  0:47 Possible bug in mirror target Drew Hastings
2019-02-05 10:03 ` Zdenek Kabelac
2019-02-10 21:58   ` John Stoffel [this message]
2019-02-12 15:02     ` Zdenek Kabelac
2019-02-12 22:36       ` John Stoffel
2019-02-13 14:21         ` Zdenek Kabelac
2019-02-13 15:01           ` Bryn M. Reeves
2019-02-13 18:08             ` Zdenek Kabelac
2019-02-14 10:23               ` Bryn M. Reeves

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