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imidge Absent Member.
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HP-UX Metrocluster and DP device usage

Hi all. We are in the process of setting up a HP-UX Metrocluster to run SAP. Each SAP module will be in its own package and will be able to fail over from one datacenter to another. The datacenters are approximately 20km apart and connected by diversely routed high speed links. There will be backup devices in each datacenter and we do not want backup data traversing the inter-site links. Data Protector will be used to backup the environment using filesystem and DB2 online integrated backups. Cell Manager will be Windows. When the package is running on nodes in DC1 we can configure the backup to target devices in DC1. However when it fails over to DC2 it is our understanding that the backup specification will still try to use the devices in DC1, which would mean the data would be transferred across the links. How do we configure DP to use the backup devices local to where the package is running?

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Absent Member.. Zigoze Absent Member..
Absent Member..

Re: HP-UX Metrocluster and DP device usage

well, if you have your servers in site 1 and site 2 in a cluster, when you configure a backup you would normally configure your backup through the virtual ip that follows the service... in that case, and in case of a failover of the service to site 2, then yes, dp would send the data to the configured device on site 1...

 

this might not be the best solution, but I believe that one way for you to workaround this issue would be to have two backups configured, one with the phisical host on site one and the local device on site one, and other with phisical host on site two and local device on site two... the problem is that you would have always a backup failling, as your service is on node on site one, and you would be trying to perform a backup on site two as well although the sap service is not on that node...

 

but this is just a thought... there must be better ways, surelly...

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imidge Absent Member.
Absent Member.

Re: HP-UX Metrocluster and DP device usage

Yes we had considered that and I agree it isn't a great solution. We have also considered not presenting devices on site1 to the noeds on site2 and vice versa. Using the media server via the package name/IP we were expecting (hoping) that DP would try the first device, timeout and then use the next device which we could configure to be in site2. However testing suggests that DP is 'clever' and if it can't find the first device via it's preferred media server (multipath host) then it tries to connect to it via the Cell Manager which is even worse as then we have data going over the LAN side of the inter-site link and then over the SAN to the device. Grrr. Hopefully someone else will have been here before.

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Absent Member.. Zigoze Absent Member..
Absent Member..

Re: HP-UX Metrocluster and DP device usage

if you configure that way, yes that would happen. you would have your backups flowing through LAN either to your cell manager or to the next multipath device you have on your list order... (on the device properties you can determine wich device path priority you want to use first by pulling up or down with the arrows beside the paths).
but, if you might be thinking that this could solve your problem by putting the other node as second on priority, it wouldn't... because the backup would always start on the first node if that node is still alive (responding to pings, although the service had passed to the other node), and so, the backup would go through LAN yes, but to your first node, and then to tape... but it would be a solution if the first node actualy died... then it would start your backup media agent on the second node...

honestly, I do not see a clean way to do this, besides the sugestion I first gave you.
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Absent Member.. Zigoze Absent Member..
Absent Member..

Re: HP-UX Metrocluster and DP device usage

I was thinking, and a "crazy" (or not so crazy) thought came to my mind...

If have a way of creating a script that cheks on wich node the service is running (i am not a SAP expert, so I cannot help you with that), then you could do a scripted solution...

something like:

- check which node has the service;
- condition that (if service = node1 then run job node1) by using the omnib command starts the backup specification on the first node;
- condition that (else run job node2), that would be started on node2);

You could then use that script as a pre-exec on Data Protector, for exemple, on a job that backs up an empty directory, but kickstarts your backup specification on the right node with the pre-exec script...

I don't know if I explained my idea suficiently clear...
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imidge Absent Member.
Absent Member.

Re: HP-UX Metrocluster and DP device usage

Yes, your explanation was sufficiently clear. I was hoping that I would get more responses. What we have decided to do is to hook an event on the Metrocluster that fires when the package moves, and use that to call a job on the Cell Manager that will copy a datalist file from a folder of our choosing to the DP datalist folder so the next time the backup triggers it will use the correct file. Not very elegant I'm afraid. Would be nice if DP was clever enough to enumerate all devices on the preferred media server and then choose one it could access. The device seems to have a higher priority than the media server, as in DP will search all media servers for a route to device 1 even when device 2 is accessible via the preferred media server and is just as good a device to use as 1.
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imidge Absent Member.
Absent Member.

Re: HP-UX Metrocluster and DP device usage

Yes, your explanation was sufficiently clear. I was hoping that I would get more responses. What we have decided to do is to hook an event on the Metrocluster that  fires when the package moves, and use that to call a job on the Cell Manager that will copy a datalist file from a folder of our choosing to the DP datalist folder so the next time the backup triggers it will use the correct file. Not very elegant I'm afraid. Would be nice if DP was clever enough to enumerate all devices on the preferred media server and then choose one it could access. The device seems to have a higher priority than the media server, as in DP will search all media servers for a route to device 1 even when device 2 is accessible via the preferred media server and is just as good a device to use as 1.  Need a check box saying Use preferred Multipath Host only. 

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