(2009-06-06) High Availability For ILM 2007 Sync Engine With Clustering
Posted by Jorge on 2009-06-06
When using ILM 2007 Sync Engine and you would like to have high availability you need to think about the all components of the solution. In the case of ILM 2007 Sync Engine those would be:
- Windows Server
- ILM 2007 Sync Engine
- SQL Server
- ILM Datastore
Windows Server and SQL Server can be made high available through Microsoft Clustering Services.
ILM Datastore can be made high available by putting it on a SAN/NAS/Shared Storage/Whatever, as long as you use a redundant set of disks, or in other words some RAID configuration such as RAID1 (mirroring), RAID5 (disk striping with parity) or RAID10 (mirroring and striping).
OK, but how about the ILM 2007 Sync Engine? For ILM 2007 Sync Engine you have following possibilities:
- Operational Instance: the ILM instance which is actually running by importing, exporting and synching data between connected data sources (ILM server license needed)
- HOT Standby Instance: the ILM instance which is NOT running (service = stopped and disabled), but for which its Windows Server is up and running (additional ILM server license needed). For a guide on how to implement this go here.
- COLD Standby Instance: the ILM instance which is NOT running (service = stopped and disabled), but for which its Windows Server is ALSO NOT up and running (NO additional ILM server license needed)
So, when the Operational Instance dies for whatever reason, use need to use the available standby instance (for the COLD standby instance you need to start the server first of course) and activate it by using the MIISACTIVATE tool with the Encryption Keys created by the first ILM instance that was installed for the solution. If you are using password synchronization (PCNS) you need to reconfigure the PCNS object in AD to target the new ILM instance. As you can see that is a manual process. Can you automate it? That depends if you are using something that can automatically switch over to the standby instance.
Is ILM 2007 Sync Engine cluster-aware? Nope, it is not!
Can you install the Operational Instance of ILM 2007 Sync Engine on a Cluster (e.g. the active node) and is it supported by MSFT? Yes, it can be installed on the active cluster node and that is also supported by MSFT.
Can you install the Standby Instance of ILM 2007 Sync Engine on a Cluster (e.g. the passive node) and is it supported by MSFT? Yes, it can be installed on the passive cluster node and that is also supported by MSFT.
Even on a cluster you need to manually switch to the standby instance on the passive node by activating it if the operational instance on the active node fails or becomes unavailable.
Can this be automated, so that when the active cluster node dies, ILM automatically switches over to the passive node and would that be supported by MSFT? Yes it is possible to automatically failover ILM by using the script which can be found here. But, is this supported? Unfortunately, it is NOT supported by MSFT! Also take this post into account.
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* Always evaluate/test yourself before using/implementing this!
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