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| zpat |
 Posted: Wed Jan 23, 2013 7:49 am Post subject: WMQ Multi-instance queue managers, listener ports |
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Jedi Council
Joined: 19 May 2001
Posts: 5849
Location: UK
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We are considering moving from HA/CMP to software HA (Multi-instance).
With HA/CMP - the same IP address is moved to the other node when it takes over. This makes life very simple in MQ client connection terms.
With MI - it doesn't move the IP, which presents difficulties running MQ client connected applications that don't use a CCDT and don't support multiple connection addresses, in terms of reaching a newly active node.
One solution with MI may be to "hide" the active QM's IP address behind a load-balancer like Big-IP and have it transparently switch to the new active QM when it takes over.
My question is - does the standby QM in a MI set up have its MQ listener port open or not?
Does it start the listener on active takeover and stop it when becoming standby?
If it's open all the time, how can Big IP avoid directing MQ connections to the standby node?
What I want is for Big IP to route new MQ client connections to the active queue manager only and never to the standby one. |
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| exerk |
| Posted: Wed Jan 23, 2013 8:44 am Post subject: Re: WMQ Multi-instance queue managers, listener ports |
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Jedi Council
Joined: 02 Nov 2006
Posts: 6339
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| zpat wrote: |
| Does it start the listener on active takeover and stop it when becoming standby? |
There is only one Listener, the one that is defined as an object within the queue manager, so when the 'active' node 'fails' so does the Listener.
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| mqjeff |
| Posted: Wed Jan 23, 2013 9:24 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
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You're right, MI does not move any IP addresses.
The theory behind MI queue managers is that every caller that needs to talk to the listener has *both* IP addresses as part of the connection.
This does not stop you from defining a qmgr service to manage the location of a virtual IP address, such that when the queue manager starts, it registers the virtual ip address at the current host - in the same way that HACMP moves the virtual ip address as part of the failover process.
An MI queue manager instance running in standby mode has a minimal footprint - there is just enough active to check the locks on the shared file system to make sure that the other instance of the queue manager is still running. So the listener is *not* running on the standby instance, as exerk says. |
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| zpat |
| Posted: Tue Jan 29, 2013 6:12 am Post subject: |
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Jedi Council
Joined: 19 May 2001
Posts: 5849
Location: UK
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Yes, although we would probably use BigIP to re-direct traffic.
However I have another question. If we relied upon NFS in this way - then the NFS server itself needs to be highly available.
How do people generally achieve that, without using HA/CMP (otherwise we might as well use HA/CMP on the queue manager directly)? |
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| fjb_saper |
| Posted: Tue Jan 29, 2013 8:14 pm Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20696
Location: LI,NY
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| zpat wrote: |
Yes, although we would probably use BigIP to re-direct traffic.
However I have another question. If we relied upon NFS in this way - then the NFS server itself needs to be highly available.
How do people generally achieve that, without using HA/CMP (otherwise we might as well use HA/CMP on the queue manager directly)? |
2 words: SAN & N A S 
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Last edited by fjb_saper on Wed Jan 30, 2013 5:33 am; edited 1 time in total |
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| zpat |
| Posted: Tue Jan 29, 2013 10:54 pm Post subject: |
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Jedi Council
Joined: 19 May 2001
Posts: 5849
Location: UK
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Yes, but SAN storage has to be attached to something that can provide the NFS server.
Our N A S offers NFS, but it can't do SRDF (which we need as well).
NB: I think this BB substitutes "contact admin" for N A S ! (WTF?) |
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| mqjeff |
| Posted: Wed Jan 30, 2013 8:08 am Post subject: |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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Right, so MI requires 'shared storage', and clearly at least implies that that storage is highly available.
But nothing says it has to be NFS shared storage. There are at least a couple more options listed as specifically tested and supported. And at least one option specifically mentioned as "we know this *doesn't* work". |
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| zpat |
| Posted: Thu Jan 31, 2013 12:33 am Post subject: |
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Jedi Council
Joined: 19 May 2001
Posts: 5849
Location: UK
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OK, but how would other forms of shared storage become visible to the standby instances when one host failed?
With NFS - both active and standby can see the NFS file system and file locking is used to determine who gets to play with it.
With ordinary SAN, it would need mounting on the other host and this is what HA/CMP does on failover. I don't believe it can be mounted on two hosts at the same time.
I guess GPFS may be one answer. |
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| mqjeff |
| Posted: Thu Jan 31, 2013 4:38 am Post subject: |
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Joined: 25 Jun 2008
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'Shared storage' exactly and explicitly means 'mounted on both servers at the same time'.
It absolutely does not mean 'mounted on the other server during failover'.
MI uses the shared storage to *determine* that failover *should* occur.
Therefore, MI requires that the same disk be visible *at all times* to *both* servers.
NFSv4 certainly provides this. The OTHER mentioned shared storage technologies that IBM says are supported for MI *also* provides this.
Yes, GPFS certainly provides this as well. |
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| zpat |
| Posted: Thu Jan 31, 2013 5:31 am Post subject: |
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Jedi Council
Joined: 19 May 2001
Posts: 5849
Location: UK
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I am not entirely sure what documentation you are referring to.
So what are the available storage sharing technologies for Power 7 and AIX? |
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| mqjeff |
| Posted: Thu Jan 31, 2013 5:52 am Post subject: |
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