Ravishankar N
2016-Mar-30 01:15 UTC
[Gluster-users] Automatic arbiter volumes on distributed/replicated volumes with replica 2?
On 03/30/2016 01:33 AM, Andr? Bauer wrote:> Am 24.03.2016 um 13:56 schrieb Ravishankar N: >> On 03/24/2016 04:30 PM, Andr? Bauer wrote: >>> So if you have a 4 node cluster is it realy needed to have a third >>> replica? Imho the 2 of the nodes could also be used as arbiters? >> I'm not sure I understand. The 'arbiter' volume is a special type of >> replica volume where the 3rd brick of that replica (for every replica) >> only holds metadata. So if you're asking if this brick itself can be >> co-located on a node which holds the other 'data' bricks of the volume, >> then yes that is possible. > My Question is: > > If i have 4 Nodes and use replica 2, why should i need to add 2 more > arbiter nodes, when i also have 2 (distributed) nodes which could do the > arbiter job automaticly?Again, the term 'arbiter' is used to refer to a type of replica-3 volume in gluster parlance (at least until another feature comes that uses the same terminology ;-) ). A replica-2 configuration does not have an 'arbiter'.> > Imho 4 nodes should be enough to get proper quorum even if only replica > 2 is used.There are both client and server quorums in gluster. http://gluster.readthedocs.org/en/latest/Administrator%20Guide/arbiter-volumes-and-quorum/ has more information. Thanks, Ravi> > Regards > Andr? > >> -Ravi >>> Does it make sense to open a feature request in the bugtracker? >>> >>> Regards >>> Andr? >>> >>> Am 24.03.2016 um 11:02 schrieb Ravishankar N: >>>> On 03/24/2016 02:39 PM, Andr? Bauer wrote: >>>>> Hi List, >>>>> >>>>> we just upgraded out 4 node cluster from 3.5.8 to 3.7.8. >>>>> >>>>> Because of replica 2 on all volumes i run into problems with read only >>>>> file systems of vm images when running on 3.5.x. As i know now the >>>>> solution would be to have replica 3 or at least use arbiter volumes. >>>>> >>>>> Yesterday i stumbled over this post in the list which i missed before >>>>> (damn spam filter): >>>>> >>>>> https://www.gluster.org/pipermail/gluster-users/2015-November/024191.html >>>>> >>>>> >>>>> Steve Dainard is pointing out that 3.7.x uses an automatic arbiter, >>>>> when >>>>> you have 4 nodes configured as distributed/replicated. >>>>> >>>>> Is this true? Could not find something about it in the documentation >>>>> :-/ >>>> There is no 'automatic' arbiter for replica 2. I think he was referring >>>> to the dummy node peer probed for maintaining server quorum. >>>> -Ravi >>>>> Would be nice i could save on having 2 more nodes this way. >>>>> >>>>> If not, is there a chance to see such feature in the future? >>>>> >>>>> >>>> >> >> >
André Bauer
2016-Mar-31 13:04 UTC
[Gluster-users] Automatic arbiter volumes on distributed/replicated volumes with replica 2?
OK, thanks. As i understand, quorum does not work on a 2 node replica 2 cluster. Thats the reason VM images get read only, if one node goes down. To get it work you need replica 3 and therefore a full third node or at least an arbiter. Why is this also the case when having 4 node replica 2 cluster? I use the other 2 nodes to have distributed/replicated volumes. Imho this should be enough to get proper quorum? If not, why? Imho the distribution nodes could also do the work the arbiter does in a 4 node replicated/distributed setup? Is this something thats makes sense from a technical view? If its technical possible but just no feature at the moment i would really like to see this in the future. Regards Andr? Am 30.03.2016 um 03:15 schrieb Ravishankar N:> On 03/30/2016 01:33 AM, Andr? Bauer wrote: >> Am 24.03.2016 um 13:56 schrieb Ravishankar N: >>> On 03/24/2016 04:30 PM, Andr? Bauer wrote: >>>> So if you have a 4 node cluster is it realy needed to have a third >>>> replica? Imho the 2 of the nodes could also be used as arbiters? >>> I'm not sure I understand. The 'arbiter' volume is a special type of >>> replica volume where the 3rd brick of that replica (for every replica) >>> only holds metadata. So if you're asking if this brick itself can be >>> co-located on a node which holds the other 'data' bricks of the volume, >>> then yes that is possible. >> My Question is: >> >> If i have 4 Nodes and use replica 2, why should i need to add 2 more >> arbiter nodes, when i also have 2 (distributed) nodes which could do the >> arbiter job automaticly? > Again, the term 'arbiter' is used to refer to a type of replica-3 volume > in gluster parlance (at least until another feature comes that uses the > same terminology ;-) ). A replica-2 configuration does not have an > 'arbiter'. > >> >> Imho 4 nodes should be enough to get proper quorum even if only replica >> 2 is used. > There are both client and server quorums in gluster. > http://gluster.readthedocs.org/en/latest/Administrator%20Guide/arbiter-volumes-and-quorum/ > has more information. > Thanks, > Ravi >> >> Regards >> Andr? >> >>> -Ravi >>>> Does it make sense to open a feature request in the bugtracker? >>>> >>>> Regards >>>> Andr? >>>> >>>> Am 24.03.2016 um 11:02 schrieb Ravishankar N: >>>>> On 03/24/2016 02:39 PM, Andr? Bauer wrote: >>>>>> Hi List, >>>>>> >>>>>> we just upgraded out 4 node cluster from 3.5.8 to 3.7.8. >>>>>> >>>>>> Because of replica 2 on all volumes i run into problems with read >>>>>> only >>>>>> file systems of vm images when running on 3.5.x. As i know now the >>>>>> solution would be to have replica 3 or at least use arbiter volumes. >>>>>> >>>>>> Yesterday i stumbled over this post in the list which i missed before >>>>>> (damn spam filter): >>>>>> >>>>>> https://www.gluster.org/pipermail/gluster-users/2015-November/024191.html >>>>>> >>>>>> >>>>>> >>>>>> Steve Dainard is pointing out that 3.7.x uses an automatic arbiter, >>>>>> when >>>>>> you have 4 nodes configured as distributed/replicated. >>>>>> >>>>>> Is this true? Could not find something about it in the documentation >>>>>> :-/ >>>>> There is no 'automatic' arbiter for replica 2. I think he was >>>>> referring >>>>> to the dummy node peer probed for maintaining server quorum. >>>>> -Ravi >>>>>> Would be nice i could save on having 2 more nodes this way. >>>>>> >>>>>> If not, is there a chance to see such feature in the future? >>>>>> >>>>>> >>>>> >>> >>> >> > > >-- Mit freundlichen Gr??en Andr? Bauer MAGIX Software GmbH Andr? Bauer Administrator August-Bebel-Stra?e 48 01219 Dresden GERMANY tel.: 0351 41884875 e-mail: abauer at magix.net abauer at magix.net <mailto:Email> www.magix.com <http://www.magix.com/> Gesch?ftsf?hrer | Managing Directors: Dr. Arnd Schr?der, Klaus Schmidt Amtsgericht | Commercial Register: Berlin Charlottenburg, HRB 127205 Find us on: <http://www.facebook.com/MAGIX> <http://www.twitter.com/magix_de> <http://www.youtube.com/wwwmagixcom> <http://www.magixmagazin.de> ---------------------------------------------------------------------- The information in this email is intended only for the addressee named above. Access to this email by anyone else is unauthorized. If you are not the intended recipient of this message any disclosure, copying, distribution or any action taken in reliance on it is prohibited and may be unlawful. MAGIX does not warrant that any attachments are free from viruses or other defects and accepts no liability for any losses resulting from infected email transmissions. Please note that any views expressed in this email may be those of the originator and do not necessarily represent the agenda of the company. ----------------------------------------------------------------------