On a nuts-and-bolts level, you can use centralized storage and fabric switching to allow "any to any" connectivity. Multiple platforms, servers and environments can access resources in a shared storage pool on SANs or high-end NAS systems. Ideally, you can design and implement your setup to share logical data stores across platforms. For example, legacy AIX and MVS applications might query and update the same inventory database. And administrators can allocate additional storage resources from the shared physical environment as needs change.
Most important, though, is centralized storage's zero downtime. The problems that plague distributed data storage are unlikely to occur in a centralized environment. Fewer overall storage devices, more robust management systems and centralized backup can translate into 99.999 percent uptime.
With DASD (direct-access storage device) arrays, redundant fabric switches, robust backup devices and storage-management software, your distributed-platform site can attain mainframe-level storage integrity and reliability. These technologies have been delivering in the big iron world for years--and you'll find storage vendors are more than happy to offer the goods for your Windows or Unix platforms.
Of course, all this reliability and performance comes at a higher per-megabyte cost than direct-attached drives (thanks to all the gee-whiz components), but the outlay can be offset if your situation is right. All vendors will be able to provide reliability specs for their products; be sure to get customer references in your industry so they can prove it to you.
Zero downtime is probably the most compelling reason to centralize storage, but there are less obvious cost benefits. Decreased storage reserves can generate substantial savings. All shops keep an available stockpile on each of their storage environments. A site might have 500 servers, with each one connected directly to a 50-GB RAID. The usual modus operandi is to maintain an average 20 percent reserve in each environment to handle short-term growth. It's a smart strategy, but it means a lot of unused storage on each box.