Storage Terms Glossary

Traditional hard drive recording technology where tracks do not overlap. Required for RAID arrays as it handles random writes without performance penalty. All enterprise and NAS-rated drives use CMR.

Endurance metric for SSDs. 1 DWPD means the full drive capacity can be written once per day over the warranty period. Read-intensive workloads need 1 DWPD; mixed enterprise needs 3 DWPD; write-intensive OLTP needs 3-10 DWPD.

Memory technology that detects and corrects single-bit errors automatically. Mandatory for servers running 24/7 to prevent data corruption. All server RAM on DatacenterDisk is ECC. Consumer desktop RAM is non-ECC.

Western Digital's recording technology used in Ultrastar HC550+ drives. Fully compatible with standard controllers and behaves identically to CMR. No special firmware or drivers required.

Next-generation recording technology from Seagate enabling 30TB+ capacities. Uses a laser to heat the platter during writes. Found in Seagate Exos 32TB drives. Check controller compatibility before deploying.

Measure of random I/O performance. HDDs deliver 100-200 IOPS. Enterprise NVMe SSDs deliver 100K-1M+ IOPS. Critical for databases, VMs, and transaction processing. Less relevant for sequential backup workloads.

Industry standard tape format for long-term archiving. LTO-9 stores 18TB native (45TB compressed) per cartridge at ~$5-8/TB - the cheapest storage medium available. Requires a dedicated tape drive ($2,000+). Common in broadcast, legal, and compliance archiving.

Storage tier between online (instant access SSD) and offline (tape archive). Nearline HDDs are 7200RPM drives optimised for sequential throughput at high capacity. Typical workload rating: 550TB/yr. Examples: Seagate Exos X, WD Ultrastar DC.

Interface protocol for SSDs using PCIe bus, replacing SATA for high-performance storage. Enterprise NVMe U.2/U.3 drives deliver 1M+ IOPS and 7GB/s sequential reads. Not compatible with SAS or SATA backplanes - requires NVMe-capable server or PCIe slot.

Database workload characterised by many small random reads and writes. Requires high IOPS storage - typically 10K/15K RPM SAS HDDs or enterprise NVMe SSDs. 7200RPM nearline drives are unsuitable due to high latency.

Server RAM module with a register between controller and DRAM chips. Improves stability in multi-DIMM configurations. Required for ECC operation in most server platforms. Not compatible with consumer motherboards.

Enterprise storage interface offering 12Gbps bandwidth and dual-port redundancy. Required for 10K and 15K RPM drives. Found in Dell PowerEdge, HPE ProLiant, and IBM server backplanes. Not compatible with consumer NAS without an HBA card.

Standard storage interface for consumer and enterprise nearline drives. 6Gbps maximum bandwidth (~550MB/s practical). Universal compatibility with NAS, servers, and desktops. Single-port only - no redundant path unlike SAS.

Recording technology where tracks overlap, increasing capacity but degrading random write performance. Unsuitable for RAID or ZFS. Found in some consumer drives (WD Red non-Plus, some Barracuda). Acceptable only for cold archive or write-once backup.

Total amount of data that can be written to an SSD over its lifetime. Derived from DWPD × capacity × warranty years × 365. Higher TBW means longer usable lifespan under write-heavy workloads.

Full cost of storage including purchase price, power, cooling, rack space, and replacement over 3-5 years. At enterprise scale, power and cooling can exceed hardware costs. Use our TCO Calculator to model your specific deployment.

Enterprise SSD form factor using a 2.5-inch drive with PCIe NVMe interface. Standard in datacenter servers since 2016. Backward compatible with U.3 backplanes via adapter. Being supplemented by EDSFF (E1.S, E3.S) in newer platforms.

Advanced filesystem used in TrueNAS, FreeBSD, and Linux. Features checksumming, snapshots, and built-in RAID (RAIDZ). Requires CMR drives - SMR causes severe performance issues. Benefits from ECC RAM in the host system.