Best Practices for a SYBASE ASE Cluster Edition Proof of Concept
June 11, 2010By Jeffrey Garbus
Youve taken a quick look, and decided that Sybase ASE Cluster Edition is right for you. Managing the POC requires a great deal of forethought & planning. Jeffrey Garbus shares some best practices to get you started.
Youve taken a quick look, and decided that Sybase ASE Cluster Edition is right for you. Chances are youve based your decision on one of a relatively tight list of reasons:
ASE CE takes advantage of shared-disk architecture, and OS-level clustering to provide high availability clustering. This means that if you are pointing to a cluster containing many servers, if one goes down, this is transparent to the end users because another server within the cluster can take over the workload, accessing the failed servers databases on the SAN.
Work-load distribution, via the workload manager, enables you to balance processing across multiple servers. Again, through the cluster entry point, transparent to the users, ASE routes the requests to the correct server (or to a random server for balancing purposes), once again making a single server failure a nonissue from the users perspective, as well as allowing less expensive resources to be used in a variety of situations.
The work-load distribution has a side benefit. You can also consolidate servers, running individual servers at a higher utilization rate, meaning that you can have several servers running at 60%, knowing that you have many servers to take on any peak performance, rather than having to run multiple servers each with enough peak potential.
So, decision made, its time to start thinking about the proof-of-concept (POC). As with many IT projects, your most critical success component will be planning.
Scoping the POC
The point of your POC is to demonstrate that the ASE CE will do what you intend it to do, in your environment.
More specifically, you need to identify a simple, quantifiable set of requirements. These may have to do with any of the areas mentioned above (high availability, workload management, connection migration), or may include ease of use of installation, backup/recovery, or performance.
In any case, you want to identify specific tests, and specific success criteria. Put together specific, detailed test cases, including POC objectives, functional specifications, and specific tests, all with success criteria in a good, checklist format.
There are a variety of ways of defining the scope, but here are a few basic levels:
You can check basic availability features. Use one node, and test the entry-level functions:
A step up from basic availability takes you a bit further. With two nodes, you can test Storage architecture:
The next step up would likely test the full shared disk cluster. Now, go up to 4 nodes, and work with:
Pushing the POC out to the most specific level, perhaps a 4-node test of your target production setup:
Planning the test bed
Test resources are often at a premium, so you need to make your list early; are you testing on VMs? Real separate boxes? Once youve established your success criteria during the scoping, you can work backwards to make sure you have the right equipment.
Define the complexity of your test bed based upon those criteria. You can run functional tests when you have multiple CE instances on a single physical node, even though you may not be confident as to the results of your failover tests. You can use partitioned nodes to work around resource availability.
A simple approach to a true multi-node cluster would be two nodes with a twisted-pair interconnect. For more (required) complexity you can go to a 4-node cluster with high-speed network interconnects and shared storage. Be sure to check the current supported hardware lists.
Your use cases will become your checklist; your table should be orchestrated along these lines:
Other test areas may include installation, high availability under a variety of circumstances, workload management, maintenance, job scheduling, and anything else that has driven your decision to evaluate CE.
The supported hardware list changes on an occasional basis, so make sure you check the Sybase web site to see whats currently available.
At this writing, supported platforms include:
Upgrades are supported from ASE versions:
Shared SAN storage is a requirement. The SAN must be certified for raw devices on SAN. The SAN fabric must be multi-pathed. All the data devices must be visible on all participating nodes. The disk subsystem should support SCSI-3 persistent reservation.
Multiple network interface cards (NICs) are also mandatory; you need both public access (from the clients) and high-speed private access (for intra-node communications).
Within a node, the same OS and architecture is required.
Installation and configuration
Most ASE configuration parameters will behave as you expect; individual servers will still process individual queries. In general, you will configure at the cluster level, and those configuration options will propagate to individual servers. You may, if you choose, configure individual instances, if for example all hardware doesnt match. Each server will also get its own system tempdb, which will be used by the quorum device.
The quorum contains the cluster configuration, which is in turn managed with the qrmutil utility.
There are other configuration parameters for CE, youll likely leave them at the defaults, but do take the time to read the release bulleting for the individual operating systems for any changes you might consider making.
Workload management is a new concept for a lot of DBAs, because in a standard ASE environment all the workload is directed at a single db server. Some examples of workload management include using standby replicated server for read-only queries.
Active load management requires metrics, and you are going to have to take some time to determine how to measure and manage this activity. You should expect a significant performance improvement with an active load segmentation strategy.
ASE CE is a significant new feature to the Sybase suite. Managing the POC requires a great deal of forethought & planning. Weve given you a bit of a starting point.
A 20-year veteran of Sybase ASE database administration, design, performance, and scaling, Jeff Garbus has written over a dozen books, many dozens of magazine articles, and has spoken at dozens of users groups on the subject over the years. He is CEO of Soaring Eagle Consulting, and can be reached at Jeff Garbus.