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Dell EMC Unity is one of Dell EMC’s mid-range storage array product lines. It was designed from the ground up as the next generation midrange unified storage array after the EMC VNX and VNXe series, which evolved out of the EMC Clariion SAN disk array.
The Dell EMC Unity product line includes the hybrid (flash SSD + magnetic HDD) 300/400/500/600 models, the all-flash 300F/400F/500F/600F models, and the Dell EMC Unity VSA virtual appliance deployable on vSphere. The basic enclosure for the hybrid and all-flash models is a 2U box with 25-2.5-inch drive slit expansion trays, called a Disk Processor Enclosure (DPE). A 15-drive 3.5-inch hybrid DPE variant is also available. Additional storage can be added using disk-array enclosures (DAEs), available in 2U 2.5-inch 25-drive, 3U 3.5-inch 15-drive and 3U 2.5-inch 80-drive configurations.
The first four drives in a Dell EMC Unity DPE are system drives that contain the Dell EMC Unity OE (Operating Environment). Any remaining drive space is available for storage pools, with a minimum configuration of five drives for the 300/400/500/600 models, and six drives for the 350/450/550/650 models (including the four system drives). The drive bays are accessible from the front of the rack. The storage processors (SPs), optical/twinex network ports, 10 Gb Base-T RJ45 ports, power supplies, IO module slots, backend SAS ports, management port and service port can be found in the rear of the DPE. The IO modules are configurable, supporting configurations that include 4 port 16GB Fiber Channel, 10GbE Base-T, 1GbE Base-T, 2 port 10GbE Optical (SFP+ and Twinax), 4 port 10GbE Optical (SFP+ and Twinax) and 12Gb SAS for backend expansion (Only for Dell EMC Unity 500 and 600). Dell EMC Unity supports Active Twinax cables only – there is no support for passive Twinax.
Dell EMC Unity SPs contain a built-in battery backup unit (BBU) that will supply power to the SP long enough to dump cache contents into an M.2 SSD. This cached content can be restored once power is restored or a malfunctioning SP is replaced. Each M.2 SSD also contains Dell EMC Unity OE boot image.
The Dell EMC Unity OE is based on SUSE Linux Enterprise Server (SLES). Unity provides block and file access to hosts and clients. Dell EMC Unity is an Asymmetric Active-Active array and is Asymmetric Logical Unit Access (ALUA) aware.
Dell EMC Unity’s Multicore Cache dynamically adjusts cache sizes according to the read and write operation, minimizing forced flushing when the high watermark level on the cache is reached. This functionality can be augmented through the implementation of Dell EMC’s fully automated storage tiering (FAST) cache. FAST cache monitors incoming I/O for access frequency and automatically copies frequently accessed data from the back-end drives into the cache. It can extend existing cache capacities up to 2 terabytes.
Dell EMC Unity OE provides block LUN, VMware Virtual Volumes (VVols) and NAS file system storage access. Multiple different storage resources can reside in the same storage pool, and multiple storage pools can be configured within the same DPE/DAE array. Each storage pool is tiered based on the performance characteristics of the storage technology used, with SSD-based storage at the top “extreme performance tier,” serial-attached SCSI (SAS) in the middle “performance tier” and near line SAS (NL-SAS) in the bottom “capacity tier.” RAID protection is applied at the tier level.
Dell EMC Unity uses FAST VP (Fully Automated Storage Tiering for Virtual Pools) algorithms to move “hot” (high-demand) data to SSD and “cold” (low-demand) data to NL-SAS. The policy can be adjusted using Unisphere. In-pool tiers can be expanded using any supported stripe width.
As of Dell EMC Unity OE 4.1, inline compression is available for block LUNs and VMware VMFS Datastores in all-flash pools.