A variation of the SAN Volume Controller is the SAN Integration Server, which is a SAN-in-a-box solution that contains not only the SAN Volume Controller but also switches and FAStT600 disk storage in the rack. Additional storage can be connected to the SAN Integration Server as well.
The SAN Volume Controller is a symmetrical pooling solution that provides the abstraction of storage by virtualizing the LUNs attached to the controllers to the servers that are connected. In addition to the virtualization of storage, advanced functions of point-in-time copy and remote copy are offered as options. Currently the Enterprise Storage Server and the FAStT family of storage devices are supported for attachment to the SAN Volume Controller. IBM has stated that additional storage systems will be supported later in the year and continuing through next year.
The management philosophy is to use a management appliance (an x-Series server) with management software to perform management functions for the SAN Volume Controller.
The virtualization software runs on the x-Series servers with Intel Pentium 4 processors and an embedded Linux operating system. IBM has installed custom drivers to improve performance over the native Linux I/O. The Master Console is a management appliance on an x-Series server running Windows 2000.
Caching is used to improve performance (and overcome latency). Write data is mirrored to a brother SAN Volume Controller and is held until written to disk. UPS's protect from a power outage until all data has been written.
Evaluator Group comments
The announcement of the SAN Volume Controller and the SAN Integration Server represent IBM's entry into the storage virtualization with their in-house developed solution. IBM has chosen to put the virtualization in the fabric with an in-the-data-path solution. They also have released the advanced functions of point-in-time copy and remote copy that operate at the fabric level, removing the need for subsystem-based functions. All of the values that have been realized with the previously released virtualization solutions are targeted to be done with the SAN Volume Controller. Since this is a new product and a new implementation, not all of the features of the products that have been on the market for a while are currently available. IBM has a roadmap for additional functions to be added over time.
Prior to the release of the SAN Volume Controller, IBM offered the DataCore SANsymphony system for specific requirements. The approaches to virtualization are similar but the implementations are different and DataCore has been in the market for over three years, gaining stability and a head start on features over that time. IBM will have its marketing might and the IBM name behind the product and should be very successful.
The initial thrust for IBM will be to offer the SAN Volume Controller and the SAN Integration Server to its business partners who will work with customers on virtualizing their storage in SAN. There will be more opportunities once IBM creates a program for their server and storage sales force to move the SVC into high-profile accounts and make the SVC a focus for IBM Global Services. It is not clear when IBM will initiate these activities.
The initial performance numbers look excellent for the virtualization solution. Using cache, IBM has hidden the additional latency of an in-the-data-path solution. Currently, the x-Series servers chosen don't exploit Xeon processors with hyperthreading so there should be additional performance opportunity in the future. IBM is pre-packaging the hardware and software, including the x-Series server used as a management appliance, to reduce the potential for conflict and confusion in installation.
The choice of having a separate management appliance (unfortunately called a Master Console), is interesting. The SAN Volume Controller should have enough processing power to perform those functions but the simplicity of software and management centralization provides some benefit at additional cost.
Overall, we believe that SAN Volume Controller will mature into a good solution that will provide real value to customers. The merits of doing fabric-based virtualization with an in-the-data-path solution have been proven already and a big-name vendor will be able to drive the successes to a wider base of customers. It will be important for IBM to quickly add other vendor storage attachment support and integrate with top-level management software. The integration with management software will become a key differentiator in the future.
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This was first published in May 2003