There is debate about that. Many customers may prefer to have just one storage system, avoiding specialized storage systems, like network attached storage (NAS) for file-based access or a complicated block-based storage system, such as a RAID array. A unified [or multiprotocol] storage platform combines both modes to offer a single solution -- that's the advantage that you hear most often. Many customers embrace the flexibility of unified storage, meaning that they can buy and deploy such a platform as just a file-based system. At some point later, they could redeploy the unified storage platform in a different usage mode. Users can decide what the storage system will do for them at any point in time.
Another benefit is simplicity, which is also a matter of debate. Some block storage systems can be complicated because of all the functionality they provide, along with the capabilities and technologies they employ. Most NAS systems providing only file-based access are very simple. Vendors have made a "competition" out of NAS deployment by vying to offer the shortest deployment time. A block storage deployment takes significantly longer. The challenge is to merge the complexity of block storage with the simplicity of NAS in a single platform. In reality, a majority of the unified storage systems are really NAS that vendors have added block mode support for.
But the issue of simplicity is even more complicated. A large percentage of NAS-centric unified storage platforms are iSCSI only -- vendors have basically taken a NAS system and added an iSCSI target-mode driver that executes the SCSI target-mode commands used against a particular volume (or LUN) dedicated to a specific use. In practice, the unified storage systems built on a NAS base with only iSCSI support probably would be simpler from a management standpoint. Those unified storage systems that add Fibre Channel capabilities are natively more complex because there are more high-end enterprise capabilities to contend with, compared to a typical iSCSI environment, such as masking or LUN affinity. So the actual "simplicity" depends on where the particular product came from, how it was designed and how it operates now.
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