Single-vendor approach
The single-vendor approach means that if you buy all of your storage gear from one vendor, virtualization will work just fine. EMC Corp. and IBM Corp. actively promote this road of dependency when customers buy EMC Symmetrix and IBM System Storage DS8000 storage systems and then install EMC PowerPath and IBM Subsystem Device Driver (SDD) path management software on their servers.
This path management software complements host-based virtualization by identifying the specific characteristics of the LUNs presented by EMC's and IBM's storage systems, such as which storage controller is the primary controller in a dual-active configuration, and sending IO traffic to that controller. The path management software then works with native operating system volume managers to combine storage system LUNs that are presented down two or more Fibre Channel (FC) paths so they appear to the host volume manager as the same LUN. It also provides load balancing and path failover down the different FC paths to the LUN.
But once a specific vendor's path management software is installed, it becomes more difficult to add another vendor's storage systems or network-based virtualization products. IBM's SDD software only works with IBM storage systems or IBM's network-based System Storage SAN Volume Controller (SVC) storage virtualization product. PowerPath supports EMC's Symmetrix and Clariion storage systems, as well as high-end storage from Hewlett-Packard (HP) Co., Hitachi Data Systems (HDS) and IBM.
The limited ability of path management software to work with other storage systems literally pushes users to adopt EMC's Invista or IBM's SVC to virtualize their environments. Though Invista and SVC somewhat undermine EMC's and IBM's push for companies to buy only their storage systems, organizations may end up selecting their network-based storage virtualization products based on the path management software they already have in place.
The impetus behind EMC's and IBM's network-based storage virtualization and SRM software initiatives isn't entirely about virtualizing and managing other vendors' storage systems. Part of the push to virtualize their own storage systems is to make it easier for users to migrate and place data on other vendors' storage systems owned by the user and to then use EMC's or IBM's SRM software for the ongoing end-to-end monitoring and management of the user's virtualized application, data and storage infrastructure.
According to Jim Rymarczyk, IBM fellow and chief virtualization technologist, most of the storage infrastructure costs approximately 10 years ago were associated with the acquisition of storage devices. Now as much as 70% of those costs are associated with management. While virtualization and SRM software can alleviate these management costs, trying to do end-to-end management in a heterogeneous storage network is fraught with problems.
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