How do I setup my Bunker and Secondary together?
Created: 01 Nov 2012 | Updated: 02 Nov 2012 | 6 comments
This issue has been solved. See solution.
I have just begun to use VR. I have played with setting up a bunker and a secondary but not together.
Do I have me secondary replicate from my bunker?
Do they work completely seprate?
Once testing is done and I feild this my Bunker will be in the same data center as my primary and my Secondary will be in another state.
Discussion Filed Under:
Comments 6 Comments • Jump to latest comment
A bunker is a secondary that has no data, just the SRL. A typical scenario would be:
In normal operation the primary sends writes to both the bunker and the DR site (the bunker does NOT send writes to the secondary), but if the primary site fails, then the bunker is converted to a primary and it send any outstanding writes to the DR site and when this is complete, the DR site becomes the primary and your application runs using the data at the DR site.
If the primary site and the bunker are close together, then a disaster may effect both primary and bunker, in which case you would have to accept that the DR site may be behind.
I don't think there is much point putting your bunker in the same data centre as the Primary - if you did you would need to make your bunker as independent as possible, so server in a separate rack (physically far away from primary if possible), separate power supply and the bunker SRL should use a separate array or local storage.
You need to consider what you are protecting yourself against as this does not protect zero data loss if you lose your primary data centre, so for:
A 3-node cluster gives better protection against a 2-node cluster + bunker server as in a 3-node cluster the 3rd node can actually run the application where the bunker server cannot. The advanatge of the bunker server is that it does not need to be of high spec as it does not have to run the application, so it is a bit cheaper
Mirroring JUST the SRL to another array (not using bunker replication) gives similar protection as putting a bunker SRL on a separate array as if you were to loose your primary array, if you still have one half of your SRL mirror, then in theory VVR should be able to continue and replicate outstanding writes to the DR site, so only advantage I can see of using bunker is that if you only have 1 array, then a bunker could use local storage ( you can't mirror SRL to local storage). Better protection against array loss is to mirror the whole storage to another array, but this is more expensive as it requires double the storage.
So why were you thinking of using bunker replication
Mike
UK Symantec Consultant in VCS, GCO, SF, VVR, VxAT on Solaris, AIX, HP-ux, Linux & Windows
If this post has helped you, please vote or mark as solution
Here is what I have, 2 servers running SFWHA with VCS. There are 2 disk arrays attached to these server. I also have a Domain Controller that doubles as a backup box. I am going to be adding 1 server in another state that I was going to use VR to keep the data up to date. As I already had that backup box I was going to add a bunker to that so that if there was a problem it would replicate the most current data to the other state. I must have misunderstood what the purpose of the bunker was.
My plan, if the 2 main server went down the secondary would look to the bunker for any missing data. I am looking at this as a backup and not a true disaster. Such as some kills the power to my rack on accident, as dumb as this sounds it has happened in the last year. Anyways in the event of a true disaster and my whole site is out services would move to the secondary in another state.
I have been reading the VR admin guide as I am setting up and testing so I am sure I will have a bunch more that I get stuck on. If you have any early advice for me I would love the input.
Thanks for the help.
You should put your 2 VCS nodes in separate racks so that if someone kills the power to one rack, you can failover to the 2nd VCS node in a separate rack.
I have a few questions:
Mike
UK Symantec Consultant in VCS, GCO, SF, VVR, VxAT on Solaris, AIX, HP-ux, Linux & Windows
If this post has helped you, please vote or mark as solution
1. No the 3rd node is not attached to the Disk Arrays, If redundancy would be better if it was then I could add a card and make this happen.
2. Yes the 2 arrays are mirrored through VEA
3. Currently the 3rd node only has 2 HDD for the OS, I was going to add more drives the I could replicate to.
4. Replication over IP, the 3rd node(local) will have a 1gb connection, the 4th node (other state) will be around a 1mb connection, I am still testing that.
5. All server have 16gb ram and the same CPU.
I would add a FC card to your 3rd node and zone your diskgroup used in your cluster to this 3rd node and not use bunker replication - below is a comparison against using 3rd node as a bunker if you loose both your cluster nodes.
3rd node as a bunker you will need to:
Import and recover bunker diskgroup
Deactivate bunker
3rd node with access to replicated diskgroup
Import and recover replicated diskgroup
Replication will automatically resume to replicate any outstanding writes
3rd node as a bunker, when you online application service group at DR:
RVGPri agent will do a takeover as primary diskgroup is not available
This means writes at DR will be tracked in DCM and cannot be replicated back to primary site
3rd node with access to replicated diskgroup
RVGPri agent will do a migration as primary diskgroup is available on 3rd node
This means writes at DR be replicated back to primary diskgroup on 3rd node
3rd node as a bunker you will need to:
Initiate DCM replay which means you will have to wait while data is transferred
During DCM replay, your primary diskgroup is inconsistent as DCMs are bitmaps and do not record the order of thw writes like the SRL
If you loose your DR node during DCM replay, you cannot fail to primary site as diskgroup is corrupt and your only option would be to revert to a backup or a snapshot if you took one before the DCM replay
After DCM replay, you will need to reactivate the bunker
3rd node with access to replicated diskgroup
Replication is already in place so you just need to switch diskgroup to cluster nodes to resume
UK Symantec Consultant in VCS, GCO, SF, VVR, VxAT on Solaris, AIX, HP-ux, Linux & Windows
If this post has helped you, please vote or mark as solution
Thanks for all the advice, I am going to try each idea and see what works the best. Getting another HBA for the 3rd node is no problem so I will start there.
Would you like to reply?
Login or Register to post your comment.