Hi again,
I have been testing and reading up on other solutions
and just wanted to check if my ideas are ok.
I have been looking at dispersed volumes and wonder if there are any
problems running replicated-distributed cluster on the master node and
a dispersed-distributed cluster on the slave side of a geo-replication.
Second thought, running disperesed on both sides, is that a problem
(Master: dispersed-distributed, slave: dispersed-distributed)?

Many thanks in advance!

Best regards
Marcus


On Thu, Feb 08, 2018 at 02:57:48PM +0530, Kotresh Hiremath Ravishankar wrote:
> Answers inline
> 
> On Thu, Feb 8, 2018 at 1:26 PM, Marcus Pedersén <marcus.peder...@slu.se>
> wrote:
> 
> > Thank you, Kotresh
> >
> > I talked to your storage colleagues at Open Source Summit in Prag last
> > year.
> > I described my layout idea for them and they said it was a good solution.
> > Sorry if I mail you in private, but I see this as your internal matters.
> >
> > The reason that I seem stressed is that I have already placed my order
> > on new file servers for this so I need to change that as soon as possible.
> >
> > So, a last double check with you:
> > If I build the master cluster as I thought from the beginning,
> > distributed/replicated (replica 3 arbiter 1) and in total 4 file servers
> > and one arbiter (same arbiter used for both "pairs"),
> > and build the slave cluster the same, distributed/replicated (replica 3
> > arbiter 1)
> > and in total 4 file servers and one arbiter (same arbiter used for both
> > "pairs").
> > Do I get a good technical solution?
> >
> 
>      Yes, that works fine.
> 
> >
> > I liked your description on how the sync works, that made me understand
> > much
> > better how the system works!
> >
> 
> Thank you very much for all your help!
> >
> 
>  No problem. We are happy to help you.
> 
> >
> > Best regards
> > Marcus
> >
> >
> > On Wed, Feb 07, 2018 at 09:40:32PM +0530, Kotresh Hiremath Ravishankar
> > wrote:
> > > Answers inline
> > >
> > > On Wed, Feb 7, 2018 at 8:44 PM, Marcus Pedersén <marcus.peder...@slu.se>
> > > 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.peder...@slu.se>
> > > > > 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@gluster.org
> > > > > > 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
> >
> > --
> > **************************************************
> > * 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

-- 
**************************************************
* 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      *
**************************************************
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