iTera Goes XSM with Echo2

Published: April 18, 2006

by Alex Woodie

At the turn of the millennium, a young company called iTera took a chance on an unproven IBM technology called remote journaling to build its OS/400 high availability solution upon. That gamble paid off handsomely, and iTera has enjoyed tremendous success over the last couple of years. Last week the growing company unveiled support for another promising high availability technology developed by IBM called Cross Site Mirroring (XSM), but can iTera recreate the magic a second time?

Cross Site Mirroring (XSM) is a new technology that gives iSeries shops another way to replicate data to off-site backup machines. The technology, which was introduced in 2004 with OS/400 V5R3 and is a form of clustering, works by mirroring one independent Auxiliary Storage Pool (iASP)--another relatively recent Rochester creation--to a second iASP running on a remote machine. XSM is the next step up from the switch-disk capability of iASPs, in which a disk or a set of disks can be made available to processors, or taken offline, while OS/400 and its applications are still running. A key difference is these iASPs can reside on different systems, whereas switched-disk only works within a single system.

The main advantage of XSM is that it's IBM's technology ensuring that the two iASPs are kept up-to-date with the latest data. As with remote journaling before it, by baking XSM down into the microcode "plumbing" of the architecture, it has the least impact on system resources, as the thinking goes, and lessens the chance of screwing things up above ground (or the OS layer) by requiring application vendors to successfully implement its APIs. Other benefits of iASP virtualization technology in general (including XSM) are that it prevents users from having to restart their machines in some cases and it can all be done without buying additional licenses for OS/400. It also has the backing of IBM, which is no small thing.

What's most important about XSM from a technology point of view is it facilitates a "machine-to-machine discussion" between iSeries, says Rick Ayres, vice president of business development for iTera. "It will help customers who feel they need a machine-driven replication facility, whereas our products are logical" and sit above the OS layer, he says. "XSM support in Echo2 gives us the ability to manage and participate in XSM and switched disk. As IBM continues to improve the switch disk and iASP capability, we built additional functionality in this last release that more easily supports that."

iTera is cautiously moving forward in adopting new technology, and XSM is no exception, Ayres says. "It's all part of the evolving resilience story from an iSeries platform standpoint that's important for us to participate in as a business partner, and important for customers to look at in the long term, especially the larger customers," Ayres says. "It's clear this is where IBM is taking the product. It's also evident from a marketplace perspective. We just did a recent trial in a bank in the U.K. They want to use XSM for one thing, use us for the rest of it."

iTera was one of the first high availability software vendors to support remote journaling, and it deserves much (but not all) of the credit for popularizing it as a data transport method within a high availability framework. It's ironic that the biggest high availability software vendors of the late 1990s were instrumental in getting IBM to add remote journaling to the OS/400 platform, and then largely ignored it in practice, as iTera and others exploited the opportunity to begin offering less expensive high availability solutions to small and midsize OS/400 shops. Will the same thing happen again with XSM?

iTera is on the leading edge with support for XSM, as it was with remote journaling, but it's not the first vendor to support the nascent technology. That honor goes to Lakeview Technology, a Chicago software company that added support for XSM to its MIMIX software nearly two years ago (see "Lakeview Says XSM Shows Promise As Young Technology for HA").

While XSM holds promise as a new way to replicate data between iSeries, it is still too early to tell if it will take off the way remote journaling did. Some of the drawbacks of XSM are it is somewhat complicated to set up (something that products from vendors like iTera may help alleviate), and it doesn't offer the same flexibility you would get with basic journaling. Because data replicated with XSM can only be used for resiliency, OS/400 shops can't use the technology to cut downtime due to backups, or for other uses. At this time, XSM is primarily a technology only the biggest iSeries shops can use.

Support for XSM and the switched-disk capability of iASPs are available in Echo2 HA Enterprise Edition, a new edition of its flagship Echo2 high availability product announced last week. At the same time, the Salt Lake City, Utah, company introduced a second-level product called Echo2 HA Edition, which is the same as the Enterprise Edition except that it lacks support for XSM and switched-disk.

iTera also unveiled a third product last week called Echo2 DR. Echo2 DR is a disaster recovery solution geared toward customers looking for a faster and more reliable backup solution than tape can provide, but who don't need a full high availability solution and the added cost that a second iSeries system entails.

Echo2 DR is largely based on an existing iTera offering called GuardianSave (see "iTera Goes 'High Availability Lite' With GuardianSave"), and combines OS/400 journaling and save-while-active features to substantially reduce the amount of downtime users need to perform backups or do regular maintenance. The software works by sending iSeries backup data to a secondary computer, which doesn't have to be an iSeries--in fact, iTera favors bargain-basement Linux PCs for the task.

iTera says Echo2 DR's use of journaling allows it to restore data right up to the point of failure. Because all changed data that's journaled is captured by Echo2 DR, the solution can restore the data and transactions entered into a user's system after its last save, which translates into a pretty good recovery point objective (RPO)--better than any tape system can offer, and rivaling the resiliency offered by high availability solutions. Keep in mind, however, that this is strictly data. It doesn't include objects, such as user profiles, that are necessary for rebuilding a failed system. And because a recovery with Echo2 DR would likely involve bringing in a new machine and rebuilding the system, it doesn't offer the same recovery time objective (RTO).

All three products are available now. For more information, visit www.iterainc.com.