Wikipedia
Celerra is a discontinued NAS device produced by EMC Corporation, available either as an integrated unit or as a NAS header which can be added to an independent EMC storage array such as a Clariion or a Symmetrix. It supports the SMB, NFS, FTP, NDMP, TFTP and MPFS protocols. A Celerra Unified Storage device use Clariion storage array as its storage layer and also provides iSCSI and Fibre Channel block-level storage.
Celerra was promoted as a platform for virtualization
Optional features included de-duplication, replication, NDMP and storage tiering.
Celerra runs on real-time operating system called Data Access in Real Time (DART). DART is a modified UNIX embedded kernel (just 32Mb) with additional functionality like Fibre Channel driver for HBA and Bonding For Ethernet added to operate as a file server.
Celerra is a based on the same X-blade architecture as the Clariion. It is available with a single data mover X-blade or with multiple data movers in an active-passive N+1 configuration.
Comparable to Celerra products are products from NetApp which offer similar features and protocol support, apart from the ability to use block-level Fibre Channel.
In 2011, EMC introduced the new VNX series of unified storage disk arrays intended to replace both Clariion and Celerra products. In early 2012, Clariion and Celerra were discontinued.