9 Jun
2020
9 Jun
'20
3:55 p.m.
I did promote the non-primary image, or I couldn't disable the image mirror.
Jason Dillaman <jdillama(a)redhat.com> 于2020年6月9日周二 下午7:19写道：
On Mon, Jun 8, 2020 at 11:42 PM Zhenshi Zhou
<deaderzzs(a)gmail.com> wrote:
I have just done a test on rbd-mirror. Follow the steps:
1. deploy two new clusters, clusterA and clusterB
2. configure one-way replication from clusterA to clusterB with
rbd-mirror
3. write data to rbd_blk on clusterA once every 5
seconds
4. get information with 'rbd mirror image status rbd_blk', the "state"
is "up+replaying"
5. demote image on clusterA(just wanna stop
syncing and switch client
connection to clusterB)
The result is:
1. I find that the "last_update" from "rbd mirror image status"
updates
every 30 seconds, which means I will lose at most 30s of data
The status updates are throttled but not the data transfer.
2. I stopped syncing on 11:02, while the data
from rbd_blk on the
clusterB is not newer than 10:50.
After demotion, you need to promote on the original non-primary side
(w/o the --force) option. It won't let you non-force promote unless it
has all the data copied. It will continue to copy data while the other
side has been demoted until it fully catches up.
Did I have the wrong steps in the switching progress?
Zhenshi Zhou <deaderzzs(a)gmail.com> 于2020年6月9日周二 上午8:57写道：
>
> Well, I'm afraid that the image didn't replay continuously, which means
I have some data lost.
> The "rbd mirror image status" shows
the image is replayed and its time
is just before I demote
> the primary image. I lost about 24 hours'
data and I'm not sure whether
there is an interval
> between the synchronization.
>
> I use version 14.2.9 and I deployed a one direction mirror.
>
> Zhenshi Zhou <deaderzzs(a)gmail.com> 于2020年6月5日周五 上午10:22写道：
>>
>> Thank you for the clarification. That's very clear.
>>
>> Jason Dillaman <jdillama(a)redhat.com> 于2020年6月5日周五 上午12:46写道：
>>>
>>> On Thu, Jun 4, 2020 at 3:43 AM Zhenshi Zhou <deaderzzs(a)gmail.com>
wrote:
>>> >
>>> > My condition is that the primary image being used while rbd-mirror
sync.
>>> > I want to get the period between
the two times of rbd-mirror
transfer the
>>> > increased data.
>>> > I will search those options you provided, thanks a lot :)
>>>
>>> When using the original (pre-Octopus) journal-based mirroring, once
>>> the initial sync completes to transfer the bulk of the image data from
>>> a point-in-time dynamic snapshot, any changes post sync will be
>>> replayed continuously from the stream of events written to the journal
>>> on the primary image. The "rbd mirror image status" against the
>>> non-primary image will provide more details about the current state of
>>> the journal replay.
>>>
>>> With the Octopus release, we now also support snapshot-based mirroring
>>> where we transfer any image deltas between two mirroring snapshots.
>>> These mirroring snapshots are different from user-created snapshots
>>> and their life-time is managed by RBD mirroring (i.e. they are
>>> automatically pruned when no longer needed). This version of mirroring
>>> probably more closely relates to your line of questioning since the
>>> period of replication is at whatever period you create new mirroring
>>> snapshots (provided your two clusters can keep up).
>>>
>>> >
>>> > Eugen Block <eblock(a)nde.ag> 于2020年6月4日周四 下午3:28写道：
>>> >
>>> > > The initial sync is a full image sync, the rest is based on the
object
>>> > > sets created. There are
several options to control the mirroring,
for
>>> > > example:
>>> > >
>>> > > rbd_journal_max_concurrent_object_sets
>>> > > rbd_mirror_concurrent_image_syncs
>>> > > rbd_mirror_leader_max_missed_heartbeats
>>> > >
>>> > > and many more. I'm not sure I fully understand what you're
asking,
>>> > > maybe you could rephrase your question?
>>> > >
>>> > >
>>> > > Zitat von Zhenshi Zhou <deaderzzs(a)gmail.com>om>:
>>> > >
>>> > > > Hi Eugen,
>>> > > >
>>> > > > Thanks for the reply. If rbd-mirror constantly synchronize
changes,
>>> > > > what frequency to
replay once? I don't find any options I can
config.
>>> > > >
>>> > > > Eugen Block <eblock(a)nde.ag> 于2020年6月4日周四 下午2:54写道：
>>> > > >
>>> > > >> Hi,
>>> > > >>
>>> > > >> that's the point of rbd-mirror, to constantly replay
changes
from the
>>> > > >> primary image to
the remote image (if the rbd journal feature
is
>>> > > >> enabled).
>>> > > >>
>>> > > >>
>>> > > >> Zitat von Zhenshi Zhou <deaderzzs(a)gmail.com>om>:
>>> > > >>
>>> > > >> > Hi all,
>>> > > >> >
>>> > > >> > I'm gonna deploy a rbd-mirror in order to sync
image from
clusterA to
>>> > > >> > clusterB.
>>> > > >> > The image will be used while syncing. I'm not
sure if the
rbd-mirror
>>> > > will
>>> > > >> > sync image
>>> > > >> > continuously or not. If not, I will inform clients
not to
write data
>>> > > in
>>> > > >> it.
>>> > > >> >
>>> > > >> > Thanks. Regards
>>> > > >> > _______________________________________________
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>>> > > >> > To unsubscribe send an email to
ceph-users-leave(a)ceph.io
>>> > > >>
>>> > > >>
>>> > > >> _______________________________________________
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>>> > > >> To unsubscribe send an email to ceph-users-leave(a)ceph.io
>>> > > >>
>>> > >
>>> > >
>>> > >
>>> > >
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>>>
>>>
>>>
>>> --
>>> Jason
>>>
--
Jason