IBM Augments PowerHA with Replication Solution
Published: October 27, 2009
by Alex Woodie
IBM filled a small gap in its high availability (HA) product lineup last week with the introduction of HA Assist for i. The new offering is a logical replication solution designed to keep certain objects, such as S/36 objects, in synch between production and backup boxes. It's designed to be used by existing users of IBM's hardware-based HA offering, PowerHA, and is not a generalized logical replication software offering.
PowerHA is the new name IBM uses to refer to its shared storage clustering solution. The PowerHA offering enables fast failovers or role swaps thanks to its architecture, in which the various nodes in a cluster all have access to shared applications and data, which is stored in independent auxiliary storage pools (iASPS).
In order to move data, the PowerHA solution requires a replication solution be installed and active. PowerHA users have the choice of two SAN-based replication solutions (Metro Mirror and Global Mirror) and one Power Systems-based replication solution (Geographic Mirroring).
However, there are some types of i OS objects that are not supported on iASPs, thereby preventing System i customers from fully relying on PowerHA to conduct business as usual in the event of an unplanned interruption to their primary System i server. This is where HA Assist for i comes in.
IBM designed HA Assist for i to replicate certain types of data, notably S/36 objects and other *SYSBASE objects, that cannot be replicated by the three iASP-based hardware replication solutions mentioned above. The HA Assist for i offering uses IBM journaling technology and clustering technologies, but cannot be used as a standalone logical replication solution (that is the job of third-party providers such as Vision Solutions and even IBM's own iCluster software, which it acquired with the purchase of DataMirror a little more than two years ago).
Administrators can interact with HA Assist for i via Java or green-screen interfaces. The software includes facilities for monitoring the state of replication, for performing role swaps, and for checking the state of synchronization, as well as automatic resynchronization functions. (However, IBM also states in its announcement that it's the responsibility of the customer to ensure synchronization.) Alarms and automatic e-mail notifications are also offered with the product.
IBM says HA Assist for i is primarily intended for larger enterprises that are already familiar with logical replication. (Considering that IBM rolled out such a single-purpose replication solution also smacks of considerable pull exercised by one or more members of the influential Large User Group.) IBM adds that the product's "high speed scrape and apply" method can scale to handle large volumes, and can be ready to resynchronize objects quickly in the event of a network outage, IBM says.
There are some prerequisites to buy this product. Customers must already have two processor licenses for PowerHA for their i OS-based Power Systems servers before they can order HA Assist for i. They must also buy at least two licenses for HA Assist for i.
For more information, see Software Announcement 209-312.
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