Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-18 Thread Digimer
On 18/04/17 04:08 AM, Christine Caulfield wrote: > >> >> This isn't the first time this has come up, so I decided to elaborate on >> this email by writing an article on the topic. >> >> It's a first-draft so there are likely spelling/grammar mistakes. >> However, the body is done. >> >>

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-18 Thread Christine Caulfield
> > This isn't the first time this has come up, so I decided to elaborate on > this email by writing an article on the topic. > > It's a first-draft so there are likely spelling/grammar mistakes. > However, the body is done. > > https://www.alteeve.com/w/The_2-Node_Myth > An excellent

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-17 Thread Dimitri Maziuk
On 04/17/2017 01:50 PM, Digimer wrote: > That sounds like a use-case where a full HA cluster is overkill already. > In any case, it would be a tiny fraction of installs and would be > tangential to the 2v3+ node debate that this thread started with. A web server with a "master/development" host:

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-17 Thread Dimitri Maziuk
On 04/17/2017 01:26 PM, Eric Robinson wrote: > I'm guessing the surviving node broadcasts a gratuitous arp reply. You have to fence one node by physically removing power at which point you don't have a split brain anymore. In a split brain scenario: two nodes are up, assuming they both send

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-17 Thread Digimer
On 17/04/17 02:21 PM, Dimitri Maziuk wrote: > On 04/17/2017 01:12 PM, Ian wrote: >> >> No, I don't understand how it's relevant to the specific topic of avoiding >> split-brains, either. > >>> Take a simple example of shared-nothing read-only cluster: all you need >>> to know is that the daemon

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-17 Thread Eric Robinson
> In shred-nothing cluster "split brain" means whichever MAC address > is in ARP cache of the border router is the one that gets the traffic. > How does the existing code figure this one out? I'm guessing the surviving node broadcasts a gratuitous arp reply. -- Eric Robinson

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-17 Thread Eric Robinson
> This isn't the first time this has come up, so I decided > to elaborate on this email by writing an article on the topic. > It's a first-draft so there are likely spelling/grammar > mistakes. However, the body is done. > https://www.alteeve.com/w/The_2-Node_Myth It looks like my question

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-17 Thread Dimitri Maziuk
On 04/17/2017 01:12 PM, Ian wrote: > > No, I don't understand how it's relevant to the specific topic of avoiding > split-brains, either. >> Take a simple example of shared-nothing read-only cluster: all you need >> to know is that the daemon is bound to '*' and the floating ip is bound >> to

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-17 Thread Digimer
On 17/04/17 02:12 PM, Ian wrote: >> maybe I need another coffee? > > No, I don't understand how it's relevant to the specific topic of > avoiding split-brains, either. I suppose it's possible that I also need > coffee. I'm trying to make the connection still, honestly, but I am still lost...

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-17 Thread Ian
> maybe I need another coffee? No, I don't understand how it's relevant to the specific topic of avoiding split-brains, either. I suppose it's possible that I also need coffee. On Mon, Apr 17, 2017 at 1:45 PM, Dimitri Maziuk wrote: > On 04/17/2017 11:58 AM, Digimer

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-17 Thread Dimitri Maziuk
On 04/17/2017 11:58 AM, Digimer wrote: > ... Unless I am misunderstanding, your comment is related to > serviceability of clusters in general. I'm failing to link the contexts. > Similarly, I'm not sure how this relates to "new" vs. "best"... You can't know if *a* customer can access the

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-17 Thread Dimitri Maziuk
On 04/17/2017 11:03 AM, Digimer wrote: > On 17/04/17 11:15 AM, Dmitri Maziuk wrote: >> What you want to know is whether the customer can access the service. >> Adding more nodes does not answer that question, but since Andrew is >> writing cluster software, not providing services, that's not his

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-17 Thread Digimer
On 17/04/17 11:15 AM, Dmitri Maziuk wrote: > On 2017-04-16 15:04, Eric Robinson wrote: > >>> On 16/04/17 01:53 PM, Eric Robinson wrote: I was reading in "Clusters from Scratch" where Beekhof states, "Some >>> would argue that two-node clusters are always pointless, but that is an >>>

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-17 Thread Dmitri Maziuk
On 2017-04-16 15:04, Eric Robinson wrote: On 16/04/17 01:53 PM, Eric Robinson wrote: I was reading in "Clusters from Scratch" where Beekhof states, "Some would argue that two-node clusters are always pointless, but that is an argument for another time." What you want to know is whether the

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-16 Thread Digimer
s.org>; Eric Robinson <eric.robin...@psmnv.com> >> Subject: Re: [ClusterLabs] 2-Node Cluster Pointless? >> >> On 16/04/17 01:53 PM, Eric Robinson wrote: >>> I was reading in "Clusters from Scratch" where Beekhof states, "Some >> would argu

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-16 Thread Eric Robinson
> -Original Message- > From: Digimer [mailto:li...@alteeve.ca] > Sent: Sunday, April 16, 2017 11:17 AM > To: Cluster Labs - All topics related to open-source clustering welcomed > <users@clusterlabs.org>; Eric Robinson <eric.robin...@psmnv.com> > Subject: Re

Re: [ClusterLabs] 2-Node Cluster Pointless?

2017-04-16 Thread Digimer
On 16/04/17 01:53 PM, Eric Robinson wrote: > I was reading in "Clusters from Scratch" where Beekhof states, "Some would > argue that two-node clusters are always pointless, but that is an argument > for another time." Is there a page or thread where this argument has been > fleshed out? Most of