DataMirror Debuts Clustering for iSeries-Symmetrix Combos

by Alex Woodie

DataMirror recently announced that it is shipping a new version of its OS/400 clustering software designed to work in AS/400 and iSeries shops that use Symmetrix disk arrays manufactured by EMC as the storage devices for their servers. The iCluster for EMC Symmetrix integrates with EMC's backup and recovery facilities, TimeFinder and Symmetrix Remote Data Facility (SRDF), and gives users two different ways to keep their OS/400 applications running when disasters or other types of down time threaten the processing of transactions.

The pairing of EMC's TimeFinder and SRDF facilities with DataMirror's iCluster provides users with two different levels of application resiliency and data protection. DataMirror's iCluster is an enterprise-strength, TCP/IP-based clustering solution that allows OS/400 workloads to be spread across multiple OS/400 servers, or nodes. In clustering, if any of the servers fail, workloads can be shifted to any other node, providing a high degree of application resiliency for OS/400 servers.

EMC's TimeFinder software is used to continuously create mirror-image copies of live production data at certain points in time, which EMC calls Business Continuance Volumes, or BCVs. These BCVs can be used for testing new applications with real data, or brought out of storage to restore a database, in the event of a disaster. SRDF works with TimeFinder to replicate production data and volumes of backup data between remotely located Symmetrix disk arrays, connected via high-speed fibre optic lines. These two facilities deal with data in a more generic, non-OS/400-specific fashion, and are more of a hybrid data replication backup and recovery solution. They can provide some degree of high availability--maybe even all the availability that some OS/400 shops need--but they can't provide the same level of application awareness that clustering solutions such as those from DataMirror, Lakeview Technology, and Vision Solutions can.

DataMirror claims that its new iCluster for EMC Symmetrix will be able to provide the highest degree of application availability of any OS/400 high availability system on the market, above and beyond the hallowed 99.999 percent availability mark. They might be right. That's because iCluster for EMC Symmetrix basically combines two completely different disaster avoidance systems--two totally separate recovery databases--into one package. Of course, it's not really a single package, because you still have to buy the Symmetrix array, TimeFinder, and SRDF facilities from EMC, which entails a fair investment of time and money. However, DataMirror's argument--that this redundant approach provides a higher degree of fault tolerance than deploying either iCluster or SRDF on its own--does appear to hold water. At the same time, the number of OS/400 shops requiring this high level of system availability--or with the budgets to implement it--remains to be seen.

Besides the disaster recovery redundancy, the new integration with SRDF and TimeFinder provides DataMirror with some other good housekeeping benefits that it says will make clustering more reliable, make backups less painful, and make query and reporting applications run faster.

Clustering will be more reliable with iCluster for EMC Symmetrix than iCluster by itself, because iCluster for EMC Symmetrix will be able to make use of SRDF's ability to execute a complete system refresh before the mirroring process begins, DataMirror says. This will eliminate the need to conduct multiple partial system refreshes from a tape, and thereby provide a more reliable starting point for mirroring than the regular iCluster setup, DataMirror says.

DataMirror also says tape backups are quicker in an iCluster for EMC Symmetrix environment than in other tape backup systems used by OS/400 shops. Because TimeFinder is continually updating the recovery data files from the backup data file, which, in turn, is continuously being replicated from the production file with SRDF, OS/400 shops can create tape backups from the recovery data file, thereby keeping the application available to users during the backup.

Likewise, because EMC's utilities allow the recovery database to be available on a read-only basis as data is being mirrored, EMC Symmetrix users are able to shuffle low-priority, read-only applications, such as query and reporting applications, to the backup server, thereby saving precious system resources.

DataMirror has also announced its inclusion into the EMC Developers program, which gives business partners access to EMC APIs for SRDF, TimeFinder, and other utilities. DataMirror also says it is giving new customers a 15 percent discount on the price of iCluster for Symmetrix through September 30, 2002. For more information, visit www.datamirror.com.

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