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Often, the inclination is to look to the major players when researching replication products, but there are some startup firms offering solid alternatives. One such vendor is Kashya Inc., San Jose, CA. Aramaic in origin, the word Kashya literally means "a difficult, puzzling problem," which is a bit of a paradox because the company's product solves much of the mystery behind storage area networks (SANs) and data replication.
Kashya's KBX5000, an IP-based replication appliance, is a cost-effective alternative to array- and some host-based solutions. It's a second-generation product that comprises software delivered on commodity hardware in the form of IBM xSeries 335 blades. A typical configuration would include a KBX5000 at each site (primary and remote), but Kashya also supports pairs of clustered KBX5000s to yield a total of four KBX5000s between the two sites (see Clustered KBX5000 replication configuration).
Up and running
A standard KBX5000 configuration includes a single QLogic Fibre Channel (FC) host bus adapter (HBA) to connect to the SAN fabric, as well as a Gigabit Ethernet NIC to replicate configured volumes over an IP WAN pipe to a second KBX5000.
Kashya, or one of its professional services partners, handles the KBX5000 installation. The boxes are delivered with the application software installed; the installers do node discovery, and configure the source and target sites, as well as the consistency groups.
An out-of-band, heterogeneous app, the KBX5000 captures data destined for the managed volume by subscribing to the same multicast group as the volume. This is done by registering with the Alias Server at the FFFFF8 address in the fabric. When writes are sent to a managed volume in the multicast group, the same blocks are sent to the local KBX5000 buffer, shipped across the IP WAN to the receiving KBX5000's IP port and written to an FC-attached volume at the remote site.
As an update to the KBX4000, the KBX5000 now certifies support of active-active Window Clusters across hundreds of miles, as well as direct- attached storage (DAS). Last month, the KBX5000 also received a Solaris-ready certification from Sun.
The heterogeneous nature of the KBX5000, and its non-disruptive implementation, gives users options when deploying remote disk targets. For example, you could have an EMC Clariion with SATA drives acting as a target for a Symmetrix supporting local writes, but could reap greater savings by using a less-expensive box as the target, assuming it adheres to applicable standards.
As long as the QLogic HBA firmware is compatible with your fabric, and both support multicast groups, the KBX5000 should discover every node on the SAN by communicating with the management server in the fabric. The Gig-E port is a standard NIC interface used to deliver enveloped FC frames in IP packets.
The quality of the IP WAN pipe between the KBX5000s is of paramount importance. Performance will degrade on a "noisy" line with faulty connections, and there is increased exposure to data loss during synchronous replication due to write acknowledgements sent when the data block reaches the buffer of the local KBX5000. The WAN pipe should be a quality connection with scalable performance characteristics.
This was first published in December 2004