Answers inline
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On Wed, Feb 7, 2018 at 8:44 PM, Marcus Pedersén <marcus.pedersen@xxxxxx> wrote:
Thank you for your help!
Just to make things clear to me (and get a better understanding of gluster):
So, if I make the slave cluster just distributed and node 1 goes down,
data (say file.txt) that belongs to node 1 will not be synced.
When node 1 comes back up does the master not realize that file.txt has not
been synced and makes sure that it is synced when it has contact with node 1 again?
So file.txt will not exist on node 1 at all?
Geo-replication syncs changes based on changelog journal which records all the file operations.
It syncs every file in two steps
1. File creation with same attributes as on master via rpc (CREATE is recorded in changelog)
2. Data sync via rsync (DATA is recorded in changelog. Any further appends will only record DATA)
The changelog processing will not halt on encountering ENOENT(It thinks it's a safe error). It's not
straight forward. When I said, file won't be synced, it means the file is created on node1 and when
you append the data, the data would not sync as it gets ENOENT since the node1 is down. But if the
'CREATE' of file is not synced to node1, then it is persistent failure (ENOTCON) and waits till node1 comes back.
I did a small test on my testing machines.
Turned one of the geo machines off and created 10000 files containing one
short string in the master nodes.
Nothing became synced with the geo slaves.
When I turned on the geo machine again all 10000 files were synced to the geo slaves.
Ofcause devided between the two machines.
Is this the right/expected behavior of geo-replication with a distributed cluster?
Yes, it's correct. As I said earlier, CREATE itself would have failed with ENOTCON. geo-rep waited till slave comes back.
Bring slave node down, and now append data to files which falls under node which is down, you won't see appended data.
So it's always recommended to use replica/ec/arbiter
Many thanks in advance!
Regards
Marcus
On Wed, Feb 07, 2018 at 06:39:20PM +0530, Kotresh Hiremath Ravishankar wrote:
> We are happy to help you out. Please find the answers inline.
>
> On Tue, Feb 6, 2018 at 4:39 PM, Marcus Pedersén <marcus.pedersen@xxxxxx>
> wrote:
>
> > Hi all,
> >
> > I am planning my new gluster system and tested things out in
> > a bunch of virtual machines.
> > I need a bit of help to understand how geo-replication behaves.
> >
> > I have a master gluster cluster replica 2
> > (in production I will use an arbiter and replicatied/distributed)
> > and the geo cluster is distributed with 2 machines.
> > (in production I will have the geo cluster distributed)
> >
>
> It's recommended to use slave also to be distribute replicate/aribiter/ec.
> Choosing only distribute will cause issues
> when of the slave node is down and a file is being synced which belongs to
> that node. It would not sync
> later.
>
>
> > Everything is up and running and creating files from client both
> > replicates and is distributed in the geo cluster.
> >
> > The thing I am wondering about is:
> > When I run: gluster volume geo-replication status
> > I see both slave nodes one is active and the other is passive.
> >
> > MASTER NODE MASTER VOL MASTER BRICK SLAVE USER SLAVE
> > SLAVE NODE STATUS CRAWL STATUS
> > LAST_SYNCED
> > ------------------------------------------------------------
> > ------------------------------------------------------------
> > ---------------------------------------------------
> > gluster1 interbullfs /interbullfs geouser
> > ssh://geouser@gluster-geo1::interbullfs-geo gluster-geo2 Active
> > Changelog Crawl 2018-02-06 11:46:08
> > gluster2 interbullfs /interbullfs geouser
> > ssh://geouser@gluster-geo1::interbullfs-geo gluster-geo1 Passive
> > N/A N/A
> >
> >
> > If I shutdown the active slave the status changes to faulty
> > and the other one continues to be passive.
> >
>
> > MASTER NODE MASTER VOL MASTER BRICK SLAVE USER SLAVE
> > SLAVE NODE STATUS CRAWL STATUS
> > LAST_SYNCED
> > ------------------------------------------------------------
> > ------------------------------------------------------------
> > ----------------------------------------
> > gluster1 interbullfs /interbullfs geouser
> > ssh://geouser@gluster-geo1::interbullfs-geo N/A Faulty
> > N/A N/A
> > gluster2 interbullfs /interbullfs geouser
> > ssh://geouser@gluster-geo1::interbullfs-geo gluster-geo1 Passive
> > N/A N/A
> >
> >
> > In my understanding I thought that if the active slave stopped
> > working the passive slave should become active and should
> > continue to replicate from master.
> >
> > Am I wrong? Is there just one active slave if it is setup as
> > a distributed system?
> >
>
> The Active/Passive notion is for master node. If gluster1 master node is
> down glusterd2 master node will become Active.
> It's not for slave node.
>
>
>
> >
> > What I use:
> > Centos 7, gluster 3.12
> > I have followed the geo instructions:
> > http://docs.gluster.org/en/latest/Administrator%20Guide/Geo% 20Replication/
> >
> > Many thanks in advance!
> >
> > Bets regards
> > Marcus
> >
> > --
> > **************************************************
> > * Marcus Pedersén *
> > * System administrator *
> > **************************************************
> > * Interbull Centre *
> > * ================ *
> > * Department of Animal Breeding & Genetics — SLU *
> > * Box 7023, SE-750 07 *
> > * Uppsala, Sweden *
> > **************************************************
> > * Visiting address: *
> > * Room 55614, Ulls väg 26, Ultuna *
> > * Uppsala *
> > * Sweden *
> > * *
> > * Tel: +46-(0)18-67 1962 *
> > * *
> > **************************************************
> > * ISO 9001 Bureau Veritas No SE004561-1 *
> > **************************************************
> > _______________________________________________
> > Gluster-users mailing list
> > Gluster-users@xxxxxxxxxxx
> > http://lists.gluster.org/mailman/listinfo/gluster-users
>
>
>
>
> --
> Thanks and Regards,
> Kotresh H R
--
**************************************************
* Marcus Pedersén *
* System administrator *
**************************************************
* Interbull Centre *
* ================ *
* Department of Animal Breeding & Genetics — SLU *
* Box 7023, SE-750 07 *
* Uppsala, Sweden *
**************************************************
* Visiting address: *
* Room 55614, Ulls väg 26, Ultuna *
* Uppsala *
* Sweden *
* *
* Tel: +46-(0)18-67 1962 *
* *
**************************************************
* ISO 9001 Bureau Veritas No SE004561-1 *
**************************************************
--
Thanks and Regards,
Kotresh H R_______________________________________________ Gluster-users mailing list Gluster-users@xxxxxxxxxxx http://lists.gluster.org/mailman/listinfo/gluster-users
