6 Best Alternatives to the Western Digital Ultrastar DC HC520 8TB (2026)

How each alternative compares

Seagate Exos 26TB CMR Hard Drive

The Seagate Exos 26TB offers significantly higher storage density than the 8TB Ultrastar. You get 26TB of capacity in the same 3.5-inch form factor, which reduces the number of drives needed in your chassis. It also features a larger 512MB cache, which can improve performance during heavy random access tasks. Like the Ultrastar, it uses CMR recording and runs at 7,200 RPM. This drive is best for users who need maximum capacity per bay and do not mind the higher power draw of a larger platter stack. It sacrifices the lower cost per terabyte of smaller drives for sheer volume.

Seagate Recertified Exos X18 16TB CMR HDD

The Seagate Exos X18 16TB provides double the storage of the original 8TB drive while maintaining the same enterprise-focused specifications. It shares the 7,200 RPM rotational speed and CMR technology, ensuring consistent performance for active workloads. The 3.5-inch SATA interface ensures compatibility with existing NAS enclosures. You gain more storage space without needing additional drive bays. This option is ideal for users who want to upgrade capacity in a single drive slot while keeping the high-speed, high-reliability profile of an enterprise drive. It offers a clear path to denser storage arrays without changing your hardware setup.

Western Digital 4TB Red Plus CMR NAS Hard Drive

The Western Digital 4TB Red Plus is a smaller, slower alternative designed for home or small office NAS systems. It uses CMR technology, which matches the Ultrastar in data integrity, but it runs at 5,400 RPM instead of 7,200 RPM. This lower speed results in reduced throughput, making it less suitable for heavy enterprise workloads. It also has a 256MB cache, similar to the original. You save space and potentially power, but you lose the high-speed performance and high reliability rating of the Ultrastar. This drive is best for users with light access patterns who prioritize capacity efficiency over raw speed.

Western Digital 18TB WD Red Pro

The Western Digital 18TB WD Red Pro offers much higher capacity than the 8TB Ultrastar while targeting NAS users specifically. It maintains the 7,200 RPM speed and CMR recording technology, providing similar performance characteristics. The 256MB cache matches the original drive. You gain more than double the storage in the same physical footprint. This drive is designed for active NAS environments and offers a balance between consumer NAS features and enterprise-grade speed. It is a strong choice if you need high capacity and speed but prefer a drive marketed specifically for network-attached storage applications rather than pure data center use.

Seagate 20TB IronWolf Pro Recertified

The Seagate 20TB IronWolf Pro Recertified provides substantial storage capacity in the standard 3.5-inch form factor. It matches the Ultrastar with 7,200 RPM speed and CMR technology, ensuring consistent performance for demanding tasks. The 256MB cache is identical to the original. You get more than double the storage space, which is useful for dense storage arrays. As a recertified unit, it may offer a different warranty profile compared to the new Ultrastar. This option is best for users who prioritize high capacity and speed on a budget and are comfortable with recertified hardware for their NAS systems.

Western Digital 2TB WD Red Plus NAS HDD

The Western Digital 2TB WD Red Plus is a significantly smaller and slower drive compared to the 8TB Ultrastar. It uses CMR technology, which is the same recording method, but it operates at 5,400 RPM. The cache is much smaller at 64MB, which may impact performance under heavy loads. You lose capacity and speed, gaining only a compact, entry-level option for light NAS usage. This drive is suitable for users with very small storage needs who prioritize basic data reliability over performance. It is not a direct performance alternative but serves users who need minimal storage for simple file sharing tasks.

Quick picks

Our 7 picks

1 Best overall

Western Digital Ultrastar DC HC520 8TB CMR HDD

Best for: Enterprise NAS systems needing 8TB capacity

Storage Capacity

8TB

Form Factor

3.5 Inch

Hardware Interface

SATA

Rotational Speed

7,200 RPM

Cache Size

256MB

Recording Technology

CMR

View on Amazon: Western Digital Ultrastar DC HC520 8TB CMR HDD

The Western Digital Ultrastar DC HC520 8TB is a 3.5-inch enterprise hard drive built for continuous operation. It uses CMR recording technology and spins at 7,200 RPM, providing consistent performance for heavy workloads. The drive includes 256MB of cache and connects via SATA. This model suits users who need high reliability and stable data access for enterprise or serious NAS environments.

Pros

• 8TB storage capacity for large datasets
• 7,200 RPM rotational speed for faster data transfer
• CMR recording technology ensures stable write performance
• 256MB cache improves handling of large files

Cons

• Heavier and bulkier than 2.5-inch portable drives
• Limited to SATA interface, not NVMe
• Designed for enterprise use, not silent home offices

Good fit if

• You need high-capacity storage for a NAS
• You run heavy workloads requiring CMR reliability
• You want a drive built for 24/7 operation

Skip if

• You need silent operation for a bedroom
• You require NVMe speeds for video editing
• You have limited space for a 3.5-inch drive

Verdict: Western Digital Ultrastar DC HC520 8TB delivers enterprise-grade reliability with 7,200 RPM performance. It is ideal for users building robust NAS systems that demand consistent speed and high capacity.

2 Best premium

Seagate Exos 26TB CMR Hard Drive

Best for: high-capacity enterprise storage

Storage Capacity

26TB

Form Factor

3.5 in

Hardware Interface

SATA 6Gb/s

Rotational Speed

7200 RPM

Cache Size

512MB

Recording Technology

CMR

View on Amazon: Seagate Exos 26TB CMR Hard Drive

The Seagate Exos 26TB offers massive storage for data-intensive environments. It uses 7200 RPM rotation and CMR recording for consistent performance. The 512MB cache helps manage large file transfers efficiently. You should consider this drive if you need enterprise-grade reliability and high workload ratings for continuous operation in a 3.5-inch form factor.

Pros

• 26TB ultra-high capacity
• 7200 RPM rotational speed
• CMR recording technology
• 512MB cache size

Cons

• High capacity may be excessive for small setups
• Enterprise class may be overkill for light use

Good fit if

• You need maximum storage density
• You run continuous enterprise workloads

Skip if

• You require quiet operation for home use
• You have limited rack space

Verdict: Seagate Exos 26TB Enterprise HDD is ideal for users needing top-tier capacity and reliability for heavy data tasks.

3 Also great

Seagate Recertified Exos X18 16TB CMR HDD

Best for: High-capacity enterprise storage arrays

Storage Capacity

16TB

Form Factor

3.5 Inch

Hardware Interface

SATA 6Gb/s

Rotational Speed

7200 RPM

Recording Technology

CMR

Dimensions

5.8 × 4 × 1 inches

View on Amazon: Seagate Recertified Exos X18 16TB CMR HDD

This recertified Seagate drive offers 16TB of storage in a 3.5-inch form factor. It runs at 7200 RPM with CMR technology and a SATA 6Gb/s interface. You get consistent performance and low latency for big data applications. The six-month warranty covers replacement. It fits well in dense server racks or high-capacity NAS setups where you need reliable enterprise-grade storage.

Pros

• 16TB storage capacity for large datasets
• 7200 RPM rotational speed for faster caching
• CMR recording technology for stability
• SATA 6Gb/s hardware interface

Cons

• Six-month warranty is shorter than standard enterprise drives
• Recertified status may concern some buyers
• Heavier at 1.48 pounds than consumer drives

Good fit if

• You need high capacity in a dense rack
• You run hyperscale or big data applications
• You want CMR reliability at a lower cost

Skip if

• You require a long-term warranty
• You need a brand new drive
• You are building a quiet home office PC

Verdict: Seagate Exos X18 16TB Enterprise HDD delivers high capacity and speed for data centers. It suits IT managers managing large archives or dense storage arrays.

4 Best budget

Western Digital 4TB Red Plus CMR NAS Hard Drive

Best for: Small NAS setups needing reliable CMR storage

Storage Capacity

4TB

Form Factor

3.5"

Hardware Interface

SATA 6 Gb/s

Rotational Speed

5400 RPM

Cache Size

256 MB

Recording Technology

CMR

View on Amazon: Western Digital 4TB Red Plus CMR NAS Hard Drive

The Western Digital 4TB WD Red Plus is a 3.5-inch internal hard drive built for NAS systems. It uses CMR recording technology for reliable data integrity and includes a 256 MB cache to help manage read/write operations. With a rotational speed of 5400 RPM, it prioritizes efficiency and lower heat output over raw performance. This drive suits users who need dependable storage for light to moderate NAS workloads.

Pros

• CMR recording technology ensures stable write speeds
• 256 MB cache improves data handling
• 4TB storage capacity fits small arrays
• SATA 6 Gb/s interface for standard connectivity

Cons

• 5400 RPM speed is slower than 7200 RPM alternatives
• 4TB capacity is smaller than high-end enterprise options
• Lower rotational speed may limit performance in heavy workloads

Good fit if

• You need a reliable CMR drive for a small NAS setup
• You prioritize lower power consumption and heat over maximum speed
• You are building a budget-conscious storage array

Skip if

• You require high-performance speeds for intensive video editing
• You need more than 4TB of storage in a single drive
• You are building a large-scale enterprise server

Verdict: Western Digital 4TB WD Red Plus NAS Drive is a solid choice for users who value data reliability and efficiency over raw speed. It fits well in small NAS enclosures where CMR technology and moderate capacity are the main priorities.

5 Also great

Western Digital 18TB WD Red Pro

Best for: Active NAS users needing high speed

Storage Capacity

18TB

Form Factor

3.5-inch

Hardware Interface

SATA 6 Gb/s

Rotational Speed

7200 RPM

Cache Size

256 MB

Recording Technology

CMR

View on Amazon: Western Digital 18TB WD Red Pro

This Western Digital drive offers 18TB of capacity with a 7200 RPM rotational speed. It uses CMR recording technology and includes 256MB of cache for faster data access. The 3.5-inch form factor fits standard desktop bays. You will get reliable performance for multimedia or business use. It suits users needing high speed and large storage in a single drive.

Pros

• 18TB high capacity
• 7200 RPM rotational speed
• 256MB cache memory
• CMR recording technology

Cons

• Heavier at 1.15 pounds
• Higher power draw from 7200 RPM
• No included software suite listed

Good fit if

• You need maximum speed for active NAS workloads
• You want high capacity without multiple drives
• You prefer CMR reliability over SMR

Skip if

• You prioritize low power consumption
• You need a quieter 5400 RPM drive
• You are building a multi-bay array with smaller drives

Verdict: WD Red Pro 18TB 7200 RPM NAS Drive is the right pick if you need a single high-capacity drive with enterprise-grade speed for active NAS environments.

6 Also great

Seagate 20TB IronWolf Pro Recertified

Best for: High-capacity NAS storage on a budget

Storage Capacity

20TB

Form Factor

3.5 Inch

Hardware Interface

SATA 6Gb/s

Rotational Speed

7200 RPM

Cache Size

256MB

Recording Technology

CMR

View on Amazon: Seagate 20TB IronWolf Pro Recertified

This recertified Seagate drive offers 20TB of storage in a 3.5-inch form factor. It uses CMR technology and spins at 7200 RPM for consistent performance. The unit includes a 256MB cache and features rotational vibration sensors to maintain stability in multi-bay NAS enclosures. It is a practical option for users needing high capacity without the cost of new enterprise drives.

Pros

• 20TB storage capacity
• 7200 RPM rotational speed
• CMR recording technology
• 256MB cache size
• Rotational vibration sensors

Cons

• Six-month warranty is shorter than standard new drives
• Recertified status may concern some buyers
• Heavier build at 1.7 pounds

Good fit if

• You need maximum storage in a single bay
• You want CMR reliability for heavy workloads
• You are budget-conscious about large capacity

Skip if

• You require a full manufacturer warranty
• You prefer new units over recertified ones
• You need a smaller 4TB or 8TB drive

Verdict: Seagate IronWolf Pro 20TB Recertified HDD delivers high capacity and speed for NAS users who prioritize storage density and CMR reliability over a standard new-drive warranty.

7 Best 64mb cache

Western Digital 2TB WD Red Plus NAS HDD

Best for: Small NAS systems needing CMR reliability

Storage Capacity

2TB

Form Factor

3.5"

Hardware Interface

SATA 6 Gb/s

Rotational Speed

5400 RPM

Cache Size

64 MB

Recording Technology

CMR

View on Amazon: Western Digital 2TB WD Red Plus NAS HDD

The Western Digital 2TB WD Red Plus is a 3.5-inch internal hard drive designed for small or medium business NAS systems. It uses CMR technology and runs at 5400 RPM with 64 MB of cache. The drive supports SATA 6 Gb/s interfaces and handles workloads up to 180 TB per year. It fits up to 8 bays and includes NASware firmware for compatibility in 24x7 environments.

Pros

• CMR recording technology for reliable data integrity
• NASware firmware ensures compatibility with NAS systems
• Supports up to 8 bays in your setup
• 180 TB/yr workload rate limit for steady use

Cons

• 2TB capacity is small compared to 16TB or 26TB alternatives
• 5400 RPM speed is slower than 7200 RPM drives
• Only includes a 3-year limited warranty

Good fit if

• You need a budget-friendly drive for light NAS tasks
• You require CMR technology for data safety
• You are building a small 2-bay NAS system

Skip if

• You need high capacity for large media libraries
• You want faster 7200 RPM performance
• You require a longer warranty period

Verdict: Western Digital 2TB WD Red Plus NAS HDD is a solid entry-level option for users prioritizing CMR reliability over raw speed or capacity. It suits small NAS builds where budget and data consistency matter more than large storage volume.

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Frequently asked questions