From: Mikulas Patocka <mpatocka@redhat.com>
To: "Tomas Dalebjörk" <tomas.dalebjork@gmail.com>
Cc: LVM general discussion and development <linux-lvm@redhat.com>,
Zdenek Kabelac <zkabelac@redhat.com>
Subject: Re: [linux-lvm] exposing snapshot block device
Date: Mon, 7 Sep 2020 09:09:08 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.2009070907110.5779@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <0B002628-0740-4DA4-A9BD-320A743A7A30@gmail.com>
[-- Attachment #1: Type: TEXT/PLAIN, Size: 2030 bytes --]
On Fri, 4 Sep 2020, Tomas Dalebjörk wrote:
> hi
> I tried to perform as suggested
> # lvconvert —splitsnapshot vg/lv-snap
> works fine
> # lvconvert -s vg/lv vg/lv-snap
> works fine too
>
> but...
> if I try to converting cow data directly from the meta device, than it doesn’t work
> eg
> # lvconvert -s vg/lv /dev/mycowdev
> the tool doesn’t like the path
> I tried to place a link in /dev/vg/mycowdev -> /dev/mycowdev
> and retried the operations
> # lvconveet -s vg/lv /dev/vg/mycowdev
> but this doesn’t work either
>
> conclusion even though the cow device is an exact copy of the cow
> device that I have saved on /dev/mycowdev before the split, it wouldn’t
> work to use to convert back as a lvm snapshot
>
> not sure if I understand the tool correctly, or if there are other
> things needed to perform, such as creating virtual information about the
> lvm VGDA data on the first of this virtual volume named /dev/mycowdev
AFAIK LVM doesn't support taking existing cow device and attaching it to
an existing volume. When you create a snapshot, you start with am empty
cow.
Mikulas
> let me know what more steps are needed
>
> beat regards Tomas
>
> Sent from my iPhone
>
> On 7 Nov 2019, at 18:29, Tomas Dalebjörk <tomas.dalebjork@gmail.com> wrote:
>
> Great, thanks!
>
> Den tors 7 nov. 2019 kl 17:54 skrev Mikulas Patocka <mpatocka@redhat.com>:
>
>
> On Tue, 5 Nov 2019, Tomas Dalebjörk wrote:
>
> > Thanks,
> >
> > That really helped me to understand how the snapshot works.
> > Last question:
> > - lets say that block 100 which is 1MB in size is in the cow device, and a write happen that wants to something or all data on that region of block
> 100.
> > Than I assume; based on what have been previously said here, that the block in the cow device will be overwritten with the new changes.
>
> Yes, the block in the cow device will be overwritten.
>
> Mikulas
>
> > Regards Tomas
>
>
>
next prev parent reply other threads:[~2020-09-07 13:09 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-22 10:47 [linux-lvm] exposing snapshot block device Dalebjörk, Tomas
2019-10-22 13:57 ` Zdenek Kabelac
2019-10-22 15:29 ` Dalebjörk, Tomas
2019-10-22 15:36 ` Zdenek Kabelac
2019-10-22 16:13 ` Dalebjörk, Tomas
2019-10-23 10:26 ` Zdenek Kabelac
2019-10-23 10:56 ` Tomas Dalebjörk
2019-10-22 16:15 ` Stuart D. Gathman
2019-10-22 17:02 ` Tomas Dalebjörk
2019-10-22 21:38 ` Gionatan Danti
2019-10-22 22:53 ` Stuart D. Gathman
2019-10-23 6:58 ` Gionatan Danti
2019-10-23 10:06 ` Tomas Dalebjörk
2019-10-23 10:12 ` Zdenek Kabelac
2019-10-23 10:46 ` Zdenek Kabelac
2019-10-23 11:08 ` Gionatan Danti
2019-10-23 11:24 ` Tomas Dalebjörk
2019-10-23 11:26 ` Tomas Dalebjörk
2019-10-24 16:01 ` Zdenek Kabelac
2019-10-25 16:31 ` Tomas Dalebjörk
2019-11-04 5:54 ` Tomas Dalebjörk
2019-11-04 10:07 ` Zdenek Kabelac
2019-11-04 14:40 ` Tomas Dalebjörk
2019-11-04 15:04 ` Zdenek Kabelac
2019-11-04 17:28 ` Tomas Dalebjörk
2019-11-05 16:24 ` Zdenek Kabelac
2019-11-05 16:40 ` Mikulas Patocka
2019-11-05 20:56 ` Tomas Dalebjörk
2019-11-06 9:22 ` Zdenek Kabelac
2019-11-07 16:54 ` Mikulas Patocka
2019-11-07 17:29 ` Tomas Dalebjörk
2020-09-04 12:09 ` Tomas Dalebjörk
2020-09-04 12:37 ` Zdenek Kabelac
2020-09-07 13:09 ` Mikulas Patocka [this message]
2020-09-07 14:14 ` Dalebjörk, Tomas
2020-09-07 14:17 ` Zdenek Kabelac
2020-09-07 16:34 ` Tomas Dalebjörk
2020-09-07 16:42 ` Zdenek Kabelac
2020-09-07 17:37 ` Tomas Dalebjörk
2020-09-07 17:50 ` Zdenek Kabelac
2020-09-08 12:32 ` Dalebjörk, Tomas
2020-09-07 19:56 ` Tomas Dalebjörk
2020-09-07 20:22 ` Tomas Dalebjörk
2020-09-07 21:02 ` Tomas Dalebjörk
2019-10-23 12:12 ` Ilia Zykov
2019-10-23 12:20 ` Ilia Zykov
2019-10-23 13:05 ` Zdenek Kabelac
2019-10-23 14:40 ` Gionatan Danti
2019-10-23 15:46 ` Ilia Zykov
2019-10-23 12:59 ` Zdenek Kabelac
2019-10-23 14:37 ` Gionatan Danti
2019-10-23 15:37 ` Zdenek Kabelac
2019-10-23 17:16 ` Gionatan Danti
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