After nearly a decade of experience installing and exploiting SAN infrastructure, it is not uncommon for a 4,000 person organization with eight to ten geographic locations to have anywhere from five to seven distinct SANs serving hundreds of applications and 1,500 - 2,000 clients. Unique tier 1 demands, pet projects, mergers and acquisitions and the like have created a situation where installed storage consists of EMC DMX’s and CLARiiON’s, HP EVA’s, IBM arrays and subsystems from a variety of server vendors including plenty of direct attached storage (DAS)—all adding up to a petabyte of capacity under management and sets of defacto tiers established along platform lines.
Each of these SANs has generally distinct hardware, storage resource management software and processes. The good news is that storage administrators can manage between 55-75 TBs per person, up from well under 10TB per admin pre-SAN. The bad news is the management edict is: “What have you done for me lately?”
Best practice for rationalizing SAN sprawl suggests:
- Clearly define recovery point objective (RPO) and recovery time objective (RTO) and let this be the driver of data placement;
- Ensure designs allow access to all tiers of storage from each server;
- Implement virtualization, creating a services layer external to the storage controller enabling the attachment of inexpensive, unintelligent arrays (rather than being held hostage to individual array software licensing practices).
Action Item: IT should collapse multiple SANs into fewer physical installations, add virtualization and data migration tools and create two or three tiers of storage so provisioning and movement can be automated. Define, agree and publish clear standards for RPO and RTO so that the storage department defines where to place data based on business needs rather than business lines defining where they want data placed.
Footnotes: Related research: Managing geometric data growth in SANs