Get control of NAS systems


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Split-path file virtualization systems separate the control and data paths, so the NAS connections and all data to/from the NAS don't pass through the file virtualization system. Split-path file virtualization is typically deployed as an x86 appliance connected to the LAN switch. They manage the namespace to direct files to the appropriate NAS or file system without intercepting any packets.


  • Nondisruptive implementation for applications/users
  • Highly scalable
  • File virtualization system failure won't cut off access to data
  • Protects current investment in NAS and file systems
  • Relatively easy file migration
  • If it uses Microsoft DFS for the namespace, DFS will always have the most recent namespace configuration allowing users and applications to access their files
  • Heterogeneous NAS support
  • Easy to operate


  • Usually requires agents on application servers and workstations for transparent file migration; agents must be managed and maintained
  • Tends to be Windows (CIFS) focused with limited NFS support

Shared-path and split-path systems are typically mutually exclusive. But EMC's Rainfinity is primarily

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a split-path system except when moving files when it's configured as shared path. That eliminates the need for split-path agents for file migrations and the shared-path scalability, performance and single-point--of-failure issues.

Shared-path systems include Avere Systems' FXT Series and F5 Network's ARX series, and EMC's Rainfinity when performing data migration. Split-path options include AutoVirt Inc.'s AutoVirt 3.0 and EMC's Rainfinity.

File virtualization systems have continued to evolve, solving more network-attached storage sprawl issues. Avere Systems' FXT automates NAS storage tiering by hosting the most active files requiring the highest performance on its system of solid-state disk and 15K rpm SAS drives. Using policies, it automatically moves files to heterogeneous back-end NAS systems based on access frequency, performance, age, etc. EMC's Rainfinity provides similar functionality within its Celerra NS NAS systems. FAST (fully automated storage tiering) on Celerra NS uses the Rainfinity engine for transparent file movement (it currently doesn't support heterogeneous systems). F5 Network's ARX uniquely solves NAS sprawl data protection by managing snapshots and replication for distributed heterogeneous NAS systems.

This was first published in February 2010

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