Hi Just a remark : perhaps it still depend on HOW corosync failed ... but in any cases, with a 3 nodes HA cluster, the quorum functionnality should be used (no-quorum-policy must be set to anything else than ignore) , meaning that one node "isolated" does not belongs to a "quorate" cluster, so it should not be authorized to fence another node. So in the worst case where the three nodes have corosync problems (and again : it is effectively a case of multiple failures !) , none of the nodes should fence any other.
Regards Alain De : "Ulrich Windl" <ulrich.wi...@rz.uni-regensburg.de> A : undisclosed-recipients:; Cc : "General Linux-HA mailing list" <linux-ha@lists.linux-ha.org> Date : 04/12/2012 08:07 Objet : [Linux-HA] Antw: Re: Corosync on cluster with 3+ nodes Envoyé par : linux-ha-boun...@lists.linux-ha.org Hi! I think it still depend on HOW corosync failed: If just some process hung or died, or the cluster network got unreachable, the node can still be fenced from remote (e.g. via SBD through FC). Regards, Ulrich >>> Digimer <li...@alteeve.ca> schrieb am 03.12.2012 um 13:13 in Nachricht <50bc976e.7040...@alteeve.ca>: > As I keep saying; If corosync dies, the cluster stack on the node fails. > So if corosync is dead, that node will not do anything; It will not > fence, it will not restart services, nothing. If you somehow lose > corosync on all nodes at the same time, then your cluster is dead. > > Clusters protect against single points of failure. Rarely can multiple > simultaneous failures be protected against. > > On 12/03/2012 07:07 AM, Hermes Flying wrote: > > I see, I will look into this. > > There is one thing I am confused about. > > If I have Node-A/Node-B/Node-C and let's say Node-A has the VIP. > > What happens if corosync fails in all nodes? Will all 3 try to kill > > eachother? > > > > > > ------------------------------------------------------------------------ > > *From:* Digimer <li...@alteeve.ca> > > *To:* Hermes Flying <flyingher...@yahoo.com> > > *Cc:* General Linux-HA mailing list <linux-ha@lists.linux-ha.org> > > *Sent:* Monday, December 3, 2012 1:20 PM > > *Subject:* Re: [Linux-HA] Corosync on cluster with 3+ nodes > > > > Most Fujitsu servers work with fence_ipmilan. I suspect the same is true > > with the IBM servers. Ask the hardware people if they have out-of-band > > management on the servers (which is the generic/marketing way of saying > > IPMI or the like). > > > > On 12/03/2012 05:00 AM, Hermes Flying wrote: > >> Some are IBM servers mentioning VMK (optional) and others are Fujitsu > >> mentioning iRMC. > >> Not sure what can I do in the IBM case > >> > >> > >> ------------------------------------------------------------------------ > >> *From:* Digimer <li...@alteeve.ca <mailto:li...@alteeve.ca>> > >> *To:* Hermes Flying <flyingher...@yahoo.com > > <mailto:flyingher...@yahoo.com>> > >> *Cc:* General Linux-HA mailing list <linux-ha@lists.linux-ha.org > > <mailto:linux-ha@lists.linux-ha.org>> > >> *Sent:* Sunday, December 2, 2012 10:36 PM > >> *Subject:* Re: [Linux-HA] Corosync on cluster with 3+ nodes > >> > >> I don't know anything about your setup or office situation, so I can't > >> speak to your specific issues. > >> > >> What I can say is that almost all actual servers have remote management; > >> Fujitsu servers have IPMI, HP servers have iLO, Dell servers have DRAC, > >> IBM servers have RSA and so on. Most generic servers have at least basic > >> IPMI. So it's very likely that you will already have what you need to > >> implement fencing. If you don't, then something like the APC AP7900 is > >> usually about $500 canadian and will work as a fence device. I don't > >> know what country you are in, so I can't speak more on availability, > >> applicability or cost. > >> > >> You might seriously want to consider hiring someone to help you with > >> this setup. Clustering is not a straight-forward topic. The cost to hire > >> a consultant might save you enough time and headache that it's cheaper > >> in the end than trying to do it yourself. > >> > >> On 12/02/2012 03:31 PM, Hermes Flying wrote: > >>> I am an application developer and so far I didn't care about HW specs > >>> (not my responsibility). > >>> Now it seems I must care and so since I am not sure what HW is being > >>> recommended for servers I will verify tomorrow and let you know. > >>> My concern is that by going to pacemaker (although seems to be exactly > >>> what I need) is that we would need to request for new HW on migrate to > >>> new deployment. I don't even know if these devices are expensive. > >>> Did you ever had an issue with this? If I have problem with this, should > >>> I be looking into different solution? Any suggestion for alternative? > >>> > >>> > >>> ------------------------------------------------------------------------ > >>> *From:* Digimer <li...@alteeve.ca <mailto:li...@alteeve.ca> > > <mailto:li...@alteeve.ca <mailto:li...@alteeve.ca>>> > >>> *To:* Hermes Flying <flyingher...@yahoo.com > > <mailto:flyingher...@yahoo.com> > >> <mailto:flyingher...@yahoo.com <mailto:flyingher...@yahoo.com>>> > >>> *Cc:* General Linux-HA mailing list <linux-ha@lists.linux-ha.org > > <mailto:linux-ha@lists.linux-ha.org> > >> <mailto:linux-ha@lists.linux-ha.org < mailto:linux-ha@lists.linux-ha.org>>> > >>> *Sent:* Sunday, December 2, 2012 10:19 PM > >>> *Subject:* Re: [Linux-HA] Corosync on cluster with 3+ nodes > >>> > >>> It must be an external device. If, for example, the kernel crashes hard, > >>> or if you get a spinlock, the system may not respond to anything or a > >>> service may never stop, blocking a reboot. You can not trust that the > >>> system is accessible or functioning in any way. > >>> > >>> Fencing *must* be an external device. Period. > >>> > >>> What kind of servers do you have? > >>> > >>> On 12/02/2012 03:15 PM, Hermes Flying wrote: > >>>> If I have a requirement not to include external HW, is there any other > >>>> way? I mean, I am not -by far- a linux expert, but how come it doesn't > >>>> do a restart or halt? > >>>> > >>>> > >>>> ------------------------------------------------------------------------ > >>>> *From:* Digimer <li...@alteeve.ca <mailto:li...@alteeve.ca> > > <mailto:li...@alteeve.ca <mailto:li...@alteeve.ca>> > >> <mailto:li...@alteeve.ca <mailto:li...@alteeve.ca> > > <mailto:li...@alteeve.ca <mailto:li...@alteeve.ca>>>> > >>>> *To:* Hermes Flying <flyingher...@yahoo.com > > <mailto:flyingher...@yahoo.com> > >> <mailto:flyingher...@yahoo.com <mailto:flyingher...@yahoo.com>> > >>> <mailto:flyingher...@yahoo.com <mailto:flyingher...@yahoo.com> > > <mailto:flyingher...@yahoo.com <mailto:flyingher...@yahoo.com>>>> > >>>> *Cc:* General Linux-HA mailing list <linux-ha@lists.linux-ha.org > > <mailto:linux-ha@lists.linux-ha.org> > >> <mailto:linux-ha@lists.linux-ha.org < mailto:linux-ha@lists.linux-ha.org>> > >>> <mailto:linux-ha@lists.linux-ha.org > > <mailto:linux-ha@lists.linux-ha.org> < mailto:linux-ha@lists.linux-ha.org > > <mailto:linux-ha@lists.linux-ha.org>>>> > >>>> *Sent:* Sunday, December 2, 2012 10:01 PM > >>>> *Subject:* Re: [Linux-HA] Corosync on cluster with 3+ nodes > >>>> > >>>> On 12/02/2012 02:56 PM, Hermes Flying wrote: > >>>>> Clear! In order to do fence and crash a node, is there a specific HW > >>>>> requirement to do this? > >>>> > >>>> Yes, there must be external hardware (out-of-band management counts as > >>>> "external", despite physically being on the server's mainboard). The > >>>> most common fence device is IPMI, iLO, RSA, iDRAC and the like. > >>>> Alternatives are switched PDUs, like APC's AP7900. > >>>> > >>>> -- > >>>> Digimer > >>>> Papers and Projects: https://alteeve.ca/w/ > >>>> What if the cure for cancer is trapped in the mind of a person without > >>>> access to education? > >>>> > >>>> > >>> > >>> > >>> -- > >>> Digimer > >>> Papers and Projects: https://alteeve.ca/w/ > >>> What if the cure for cancer is trapped in the mind of a person without > >>> access to education? > >>> > >>> > >> > >> > >> -- > >> Digimer > >> Papers and Projects: https://alteeve.ca/w/ > >> What if the cure for cancer is trapped in the mind of a person without > >> access to education? > >> > >> > > > > > > -- > > Digimer > > Papers and Projects: https://alteeve.ca/w/ > > What if the cure for cancer is trapped in the mind of a person without > > access to education? > > > > > _______________________________________________ Linux-HA mailing list Linux-HA@lists.linux-ha.org http://lists.linux-ha.org/mailman/listinfo/linux-ha See also: http://linux-ha.org/ReportingProblems _______________________________________________ Linux-HA mailing list Linux-HA@lists.linux-ha.org http://lists.linux-ha.org/mailman/listinfo/linux-ha See also: http://linux-ha.org/ReportingProblems
