Enterprise storage arrays decoded

Block vs file vs unified vs object

The single most important thing to understand about any array is how hosts talk to it.

Access type	What it serves	Protocols	Typical use
Block (SAN)	Raw volumes/LUNs the host formats itself	FC, iSCSI, NVMe/FC, NVMe/TCP	Databases, virtualisation datastores, latency-sensitive apps
File (NAS)	Ready-made shared folders	NFS, SMB/CIFS	User shares, home directories, media, general file serving
Unified	Both block and file from one system	All of the above	Consolidating SAN and NAS onto one platform
Object	Data as objects via an API	S3	Backups, archives, cloud-native and analytics data

A SAN (storage area network) array serves block; a NAS serves file; a unified array does both. Most modern midrange arrays are unified, which lets one box replace a separate SAN and separate NAS.

Flash, NVMe and how to read a capacity figure

Two more distinctions decide performance and price:

• All-flash vs hybrid vs HDD. All-flash arrays use only SSDs (or purpose-built flash modules); hybrid arrays mix flash with spinning SAS/NL-SAS disk and tier hot data onto the flash; HDD-only arrays are cheapest per terabyte for cold, bulk data.
• SAS SSD vs end-to-end NVMe. Older all-flash designs attach SSDs over 12 Gb SAS. Newer designs are end-to-end NVMe — the drives, and often the host connection (NVMe/FC, NVMe/TCP), speak NVMe for lower latency.

When you read capacity, separate raw (the drive vendor's byte count), usable (after RAID and system overhead) and effective (after data reduction). Vendors headline effective capacity assuming a data-reduction ratio — Dell and NetApp both assume 5:1 on their all-flash sheets — so always confirm the assumption before comparing two arrays.

Finally, note how an array grows: scale-up adds drives behind a fixed controller pair; scale-out clusters multiple controller nodes together for more performance as well as capacity.

The Dell family

Dell fields three distinct lines that map cleanly onto the three tiers.

PowerStore is Dell's flagship unified midrange-to-high-end platform. Every appliance has two active/active nodes and an end-to-end all-NVMe design with dual-ported NVMe SSDs and NVMe-over-fabric on both Fibre Channel and TCP. The Gen 2 range runs from the 500T (2 Intel Xeon CPUs, 24 cores, 192 GB, up to 97 drives) through the 1200T, 3200T, 5200T and up to the 9200T (4 CPUs, 112 cores, 2,560 GB). The base enclosure is 2U with 25 NVMe slots; up to three 24-drive expansion shelves attach per appliance, and up to four appliances form a cluster that scales past 23 PBe. It serves block (FC, iSCSI, NVMe/FC, NVMe/TCP), file (NFS v3/v4.x, SMB 1/2/3, FTP/SFTP) and vVols, with always-on data reduction (zero-detect, deduplication, compression), the Dynamic Resiliency Engine for single/dual-parity protection, and self-encrypting drives throughout. The Q models use QLC flash for higher capacity per rack unit.

Unity XT is Dell's prior-generation unified midrange array. It is a dual-controller (two storage processors) design offered as all-flash (F) or hybrid, built on 12 Gb SAS media rather than end-to-end NVMe. The range spans the entry 380/380F, then the 480/480F (32 cores and 192 GB of memory per array, up to 750 drives), 680/680F (48 cores, 384 GB per array, 1,000 drives) and 880/880F (64 cores, 768 GB per array, 1,500 drives). It serves block (FC, iSCSI) and file (NFS, SMB/CIFS) with inline deduplication and compression. PowerStore is its stated successor and can natively migrate Unity and Unity XT volumes and file systems, which matters when planning a refresh.

PowerVault ME5 is Dell's entry block SAN/DAS array — “Simple. Fast. Affordable.” in Dell's own words. It uses dual-active controllers (each with 8 GB of memory plus 16 GB of cache — 24 GB total per controller) and comes as the ME5012 (twelve 3.5″ bays, 2U), ME5024 (twenty-four 2.5″ bays, 2U) or the dense ME5084 (eighty-four 3.5″ bays, 5U). With expansion it scales to 336 drives and up to 8 PB. Host connectivity is 32 Gb FC (auto-negotiating to 16 Gb), 25 Gb or 10 GBase-T iSCSI, or 12 Gb SAS — eight ports per array. It supports RAID 1/5/6/10 or Dell's ADAPT distributed erasure coding, auto-tiering across up to three tiers, and all-inclusive software. It is native block only; file access requires a separate NX NAS appliance.

The HPE family

HPE Alletra Storage MP B10000 is HPE's current flagship: a disaggregated, scale-out block and file platform. The building block is a 2U enclosure with 24 NVMe SFF bays and two nodes; a system runs two to four controller nodes and grows further over a switched fabric, up to roughly 5.6 PB. Because compute and storage scale independently, you add controllers for performance or shelves for capacity as needed. Host connectivity spans 32/64 Gb Fibre Channel (SCSI and NVMe/FC) and 10/25 GbE (iSCSI and NVMe/TCP). It is managed as a service through the HPE GreenLake cloud platform.

HPE Alletra 6000 and Alletra 5000 are the direct successors to HPE Nimble Storage, carrying over Nimble's CASL architecture and HPE InfoSight analytics. The Alletra 6000 is the NVMe all-flash successor to Nimble All Flash, for business-critical block workloads; the Alletra 5000 is the hybrid-flash successor to Nimble Adaptive Flash, for cost-efficient general-purpose block storage. Both carry a six-nines (99.9999%) availability guarantee as a standard benefit. (HPE also fields the high-end Alletra 9000, from the 3PAR/Primera lineage.)

HPE MSA is HPE's long-running entry SAN line, now in its sixth generation. The MSA 2060 is a 2U dual-controller active/active block array with four host ports per controller — 16 Gb FC, 10 GbE iSCSI or 12 Gb SAS — up to 395,000 IOPS, and with current Gen6 media grows to a maximum of roughly 7.37 PB raw across nine expansion enclosures. The MSA 2062 is the same array pre-bundled with two 1.92 TB SSDs and the Advanced Data Services licence for tiering and replication on day one, while the MSA 1060 is the lowest-cost entry point, rated at over 154,000 IOPS. All use HPE's MSA-DP+ data protection, a Gen6 RAID acceleration ASIC and self-encrypting-drive options.

NetApp: AFF and FAS on ONTAP

NetApp's arrays share one operating system — ONTAP — and are natively unified, serving SAN and NAS from the same cluster: FC, iSCSI, NVMe/FC, NVMe/TCP, FCoE, NFS, SMB/CIFS and Amazon S3.

The AFF A-Series is the all-flash line with end-to-end NVMe, from NVMe SSDs to NVMe/FC and NVMe/TCP host connectivity. Grounded models run from the entry AFF A150 (2U, up to 864 SSDs, 26 PB effective) and A250, through the midrange A400, to the high-end compact A800 (4U, 48 SSDs) and flagship A900 (8U). Every model clusters from 2 to 24 nodes (12 HA pairs); a cluster can deliver up to 14.4 million IOPS and present a single NAS namespace of up to 20 PB and 400 billion files. The FAS Series is the hybrid-flash sibling on the same ONTAP software, unifying SAN and NAS with Flash Pool caching for cost-efficient capacity; the FAS500f is an all-flash entry variant. Because both run ONTAP, they replicate to each other and to NetApp's cloud services with the same tools (SnapMirror, MetroCluster, FabricPool tiering).

Pure Storage FlashArray

Pure Storage FlashArray provides unified block and file on an all-NVMe architecture, run by the Purity operating environment. Its distinguishing feature is the DirectFlash Module — Pure-designed raw-flash modules addressed directly over NVMe, rather than off-the-shelf SSDs with their own flash-translation layer. Connectivity includes NVMe-oF over Fibre Channel, RoCE and TCP, plus SMB and NFS for file. The families split by workload:

• //X — the performance line, from the //X20 (up to 314 TB effective) and //X50 (663 TB) to the //X70 (up to 2,286 TiB effective, ~2.3 PB) and //X90 (up to 3.3 PB effective / 878 TB raw), each 3U.
• //XL — the largest performance systems for the most data-intensive apps.
• //C — capacity-optimised, using TLC/QLC flash (up to 75 TB QLC modules) as a lower-cost, high-density tier.
• //E — the most cost-effective, QLC-based block-and-file option for capacity-oriented workloads.

Purity averages 5:1 data reduction (10:1 total efficiency including thin provisioning), encrypts everything by default, and is delivered under the Evergreen model of non-disruptive upgrades. Business continuity comes from ActiveCluster (synchronous active/active, zero RPO/RTO), ActiveDR and immutable SafeMode snapshots, managed from the Pure1 cloud.

The whole landscape at a glance

Array	Vendor	Access	Media	Tier	Operating environment
PowerStore (500T–9200T / Q)	Dell	Unified (block + file + vVols)	End-to-end NVMe (TLC; QLC on Q)	Midrange → high-end	PowerStoreOS
Unity XT (380–880 / F)	Dell	Unified (block + file)	All-flash or hybrid (SAS)	Entry → midrange	Unity OE
PowerVault ME5 (5012/5024/5084)	Dell	Block SAN/DAS	All-flash, hybrid or HDD (SAS)	Entry	PowerVault Manager
Alletra Storage MP B10000	HPE	Unified (block + file)	All-NVMe	Midrange → high-end	GreenLake
Alletra 6000	HPE	Block	NVMe all-flash	Midrange	InfoSight / GreenLake
Alletra 5000	HPE	Block	Hybrid flash	Entry → midrange	InfoSight / GreenLake
MSA 2060 / 2062 (Gen6)	HPE	Block SAN	Hybrid flash (SAS)	Entry	MSA SMU
AFF A-Series (A150–A900)	NetApp	Unified (SAN + NAS + S3)	End-to-end NVMe	Entry → high-end	ONTAP
FAS Series	NetApp	Unified (SAN + NAS)	Hybrid flash	Entry → midrange	ONTAP
FlashArray //X //XL //C //E	Pure Storage	Unified (block + file)	All-NVMe DirectFlash	Entry → high-end	Purity

Choosing a tier

• Entry (ME5, MSA 2060/2062, Alletra 5000): a first shared SAN for a handful of hosts, backup targets, or cost-sensitive capacity.
• Midrange (PowerStore 500T–3200T, Unity XT 480–680, Alletra 6000 / Alletra MP, AFF A150–A400, FlashArray //X20–//X50): the sweet spot for consolidating virtualisation, databases and file serving onto one unified array.
• High-end (PowerStore 9200T, Unity 880, larger Alletra MP clusters, AFF A800/A900, FlashArray //X70–//X90 / //XL): mission-critical, low-latency workloads at scale with the strongest availability guarantees.

Refurbished enterprise arrays can deliver a full tier more capability for the same budget, provided the controllers, drives and licensing are validated. Configuration, capacity and the rand all move pricing constantly, so check the current catalogue for any model above rather than working from a list price.

Enterprise storage and drives, priced in rand: