Re: [ceph-users] Two mons
There is nothing that will stop you from having an even number of mons (including 2). You just run the chance of getting into a split brain scenario. As long as you aren't planning to stay in that scenario, I don't see a problem with it. I have 3 mons in my home cluster and I've had to remove one before leaving me with 2 for a few hours while I re-provisioned the third and nothing funky happened. Most ways to deploy a cluster allow you to create the cluster with 3+ mons at the same time (inital_mons). What are you doing that only allows you to add one at a time? On Tue, Aug 15, 2017 at 12:22 PM Oscar Segarra wrote: > Hi, > > I'd like to test and script the adding monitors process adding one by one > monitors to the ceph infrastructure. > > Is it possible to have two mon's running on two servers (one mon each) --> > I can assume that mon quorum won't be reached until both servers are up. > > Is this right? > > I have not been able to find any documentation about the behaviour of the > sistem with just two monitors (or an even number of them). > > thanks a lot. > ___ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
Re: [ceph-users] Two mons
Hi David, Thanks a lot for your quick response... *What are you doing that only allows you to add one at a time?* I'm trying to create a scrip for adding/removing a mon in my environment --> I want to execute it from a simple web page... Thanks a lot! 2017-08-15 19:26 GMT+02:00 David Turner : > There is nothing that will stop you from having an even number of mons > (including 2). You just run the chance of getting into a split brain > scenario. As long as you aren't planning to stay in that scenario, I don't > see a problem with it. I have 3 mons in my home cluster and I've had to > remove one before leaving me with 2 for a few hours while I re-provisioned > the third and nothing funky happened. > > Most ways to deploy a cluster allow you to create the cluster with 3+ mons > at the same time (inital_mons). What are you doing that only allows you to > add one at a time? > > On Tue, Aug 15, 2017 at 12:22 PM Oscar Segarra > wrote: > >> Hi, >> >> I'd like to test and script the adding monitors process adding one by one >> monitors to the ceph infrastructure. >> >> Is it possible to have two mon's running on two servers (one mon each) >> --> I can assume that mon quorum won't be reached until both servers are up. >> >> Is this right? >> >> I have not been able to find any documentation about the behaviour of the >> sistem with just two monitors (or an even number of them). >> >> thanks a lot. >> ___ >> ceph-users mailing list >> ceph-users@lists.ceph.com >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >> > ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
Re: [ceph-users] Two mons
On Tue, Aug 15, 2017 at 10:28 AM David Turner wrote: > There is nothing that will stop you from having an even number of mons > (including 2). You just run the chance of getting into a split brain > scenario. > Just a note: even numbers of monitors mean that it's easier to lose quorums, but they cannot create a classic split brain (in which two sets of monitors both think they are in charge). We work very hard to avoid that situation ever arising in RADOS. :) -Greg As long as you aren't planning to stay in that scenario, I don't see a > problem with it. I have 3 mons in my home cluster and I've had to remove > one before leaving me with 2 for a few hours while I re-provisioned the > third and nothing funky happened. > > Most ways to deploy a cluster allow you to create the cluster with 3+ mons > at the same time (inital_mons). What are you doing that only allows you to > add one at a time? > > On Tue, Aug 15, 2017 at 12:22 PM Oscar Segarra > wrote: > >> Hi, >> >> I'd like to test and script the adding monitors process adding one by one >> monitors to the ceph infrastructure. >> >> Is it possible to have two mon's running on two servers (one mon each) >> --> I can assume that mon quorum won't be reached until both servers are up. >> >> Is this right? >> >> I have not been able to find any documentation about the behaviour of the >> sistem with just two monitors (or an even number of them). >> >> thanks a lot. >> ___ >> ceph-users mailing list >> ceph-users@lists.ceph.com >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >> > ___ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
Re: [ceph-users] Two mons
Thanks a lot Greg, nice to hear! 2017-08-15 21:17 GMT+02:00 Gregory Farnum : > On Tue, Aug 15, 2017 at 10:28 AM David Turner > wrote: > >> There is nothing that will stop you from having an even number of mons >> (including 2). You just run the chance of getting into a split brain >> scenario. >> > > Just a note: even numbers of monitors mean that it's easier to lose > quorums, but they cannot create a classic split brain (in which two sets of > monitors both think they are in charge). We work very hard to avoid that > situation ever arising in RADOS. :) > -Greg > > > As long as you aren't planning to stay in that scenario, I don't see a >> problem with it. I have 3 mons in my home cluster and I've had to remove >> one before leaving me with 2 for a few hours while I re-provisioned the >> third and nothing funky happened. >> >> Most ways to deploy a cluster allow you to create the cluster with 3+ >> mons at the same time (inital_mons). What are you doing that only allows >> you to add one at a time? >> >> On Tue, Aug 15, 2017 at 12:22 PM Oscar Segarra >> wrote: >> >>> Hi, >>> >>> I'd like to test and script the adding monitors process adding one by >>> one monitors to the ceph infrastructure. >>> >>> Is it possible to have two mon's running on two servers (one mon each) >>> --> I can assume that mon quorum won't be reached until both servers are up. >>> >>> Is this right? >>> >>> I have not been able to find any documentation about the behaviour of >>> the sistem with just two monitors (or an even number of them). >>> >>> thanks a lot. >>> ___ >>> ceph-users mailing list >>> ceph-users@lists.ceph.com >>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >>> >> ___ >> ceph-users mailing list >> ceph-users@lists.ceph.com >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >> > ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
