So here I am, looking at hard drives. Given that this is a budget NAS as a secondary backup, I previously looked at renewed hard drives on the market that were previously used in data centers. Given the price per terabyte ratio, the current market conditions revealed that the best prices for capacity sat around 10 to 14 TB.
Just a side note, I had mostly found the refurbished drives on Amazon, but I’ve also found that Server Part Deals also sells refurbished drives, but the prices tend to be about 20% higher.
Now I’ve got questions. Whats the difference between the different brands, and what’s the difference between the various drives that each brand offers. Some brands spell out specifically what the drive is for – but why? What’s the difference between a drive for NAS, Surveillance, or Enterprise?
Three brands stood out as I was looking at renewed drives – MDD, Seagate, and Western Digital. This is what I found about that at a quick glance.
Max Digital Data (MDD) hard drives are sold under GoHardDrive’s white label have have competitive pricing. The are sourced from new old stock (NOS) or refurbished drives that were once part of a major manufacturers line, but are o longer sold. Drives are either unused and discontinued, or reconditioned. Their long-term reliability can vary.Warranty periods tend be shorter, less support and trust compared to recognized brands like Seagate, Western Digital, or Toshiba. Support for replacements are not always readily available. Drives can be appealing for cost-conscious builds, especially for NAS systems, but carry an inherent risk due to their sourcing and lack of direct manufacturer support. The risk can be balanced with more reliable, smaller capacity drives if absolute uptime and failure resistance are crucial.
| Enterprise | High-density applications such as cloud and data centers for 24/7 operations with high reliability and efficient data access focusing on scalability and high-capacity workloads |
| Surveillance | Used for 24/7 video surveillance systems with continuous write-intensive workloads under constant operation. |
| NAS | Built for multi-user access with enhanced reliability and higher tolerance for multi-drive configurations. |
| Datacenter | Enterprise-class data centers with high capacity and speeds for large-scale server and storage systems. |
| Desktop | Personal computers with regular data storage tasks. Typically in smaller capacities and lower speeds, optimized for individual users. |
Western Digital offers Blue, Black, Red, Gold, and Purple drives.
Of special note is that WD has experienced backlash over its use of Shingled Magnetic Recording (SMR) technology in its Red NAS drives when it did not clearly disclose the use of slower SMR technology in these drives. Although SMR can increase storage density, it significantly reduces performance, especially for random write operations. SMR is less suitable for use in environments requiring high write speeds like ZFS or other RAID configurations. Some red drives still use SMR, but are typically the lower capacity models between 2-6 GB. As a response to customer concerns, WD introduced the Red Plus series which uses Conventional Magnetic Recording (CMR) across all capacities. The WD Red Pro series also uses CMR and targeted for more intensive use cases.
| Color | Target |
|---|---|
| Blue | Everyday consistent needs balancing performance, capacity, and cost. |
| Black | High-Performance gaming and power users with faster speeds and larger caching sizes |
| Red | Specifically for network attached storage using less power, enhanced error recovery, and optimized for 24/7 operation |
| Gold | Enterprise environments with high capacity and reliability with features like vibration protection and RAID optimization. More durable under heavy use and handles high workloads. |
| Purple | Designed for surveillance with continuous read/write for consistently storing video, or watching/retrieving large video streams. |
Seagate uses different drive technologies, including Heat-Assisted Magnetic Recording (HAMR) for greater capacity and performance.
| Barracuda | Desktop and consumer applications with high storage capacities and fast speeds for home users and small businesses. |
| IronWolf | Targets NAS users to handle demands of multi-user environments, optimized for 24/7 use and often used in home and small office NAS setups. They are built with AgileArray technology for better NAS performance, reliability, and health monitoring. |
| SkyHawk | Focused on surveillance systems, SkyHawk drives are tailored for video storage, supporting up to 64 HD cameras for surveillance systems. They are built to manage the high write-intensive workloads typical in security systems, offering features like AI-enhanced video streaming. |
| Exos | Enterprise-class drive for high-performance data centers and servers handling massive storage needs. Offers reliable and high-capacity storage, and used for virtualization and transactional processing. They offer optimal durability and data integrity. |
| Barracuda Pro | High speed performance for workstations and desktop environments. Faster read/write speeds and higher durability compared to the standard Barracuder line. Suitable for quick access to large files for tasks like video editing and data analysis. |
Ok… so Western Digital has had problems. The community called them out on it, and they addressed the issue. Given that I’m laser focused on the ZFS file system, I need to avoid Shingled Magnetic Recording (SMR) and look for Conventional Magnetic Recording (CMR).
What is SMR? The cost-effective technology overlaps tracks in the disk to increase areal density and maximize storage capacity. To overwrite data, they need to wipe out multiple neighboring tracks of data and rewrite them (aka re-write amplification). Extra steps are taken to avoid corrupting adjacent data. In turn, they have lower write performance. It’s more suitable for archival purposes or write-once, read-many (WORM) applications typically found in media storage such as finalized/production video.
Conventional Magnetic Recording (CMR) are better for high-performance, high-frequency random writes. They support heavy and consistent write speeds.
My drives are going to be powered 24/7, so it seems that these drives oriented towards NAS, Surveillance, and Data Centers are great for that. I’m a single person, but I have various systems running that may need to access different data throughout the day, so the drives focused on NAS seem appropriate for – a NAS. Surveillance is a tricky one. Many of my cameras have local storage as well as cloud storage. I’m uncertain if I could capture video streams from those devices and save them directly to the NAS. If I ever go in that route, it may be optimal to have a separate dedicated system to handle that, and in turn use drives specifically for that purpose. Enterprise seems appropriate as well, but will I be able to benefit from those drives vs drives focused on NAS?
Well… let’s see. I heard mentions about Shingled Magnetic Recording in the past, but wasn’t privy to the details and specific detriment to ZFS. What other technologies do hard drives use that may affect my decision on their compatibility for being used within a NAS with a ZFS file system?
Hard Drive Technologies
Time-Limited Error Recovery (TLER) limits the amount of time the drive spend trying to recover from a read or write error. This helps prevent a RAID array from failing or degrading. In normal hard drives, an error recovery can take a long time (a few minutes) as the drive continues to try and read data until successful or times out. A RAID controller may interpret the unresponsive drive as failed, and drop it from the array. TLER caps the time allowed for recovery (7-10 seconds). The problem is then handed off to the RAID controller instead, which can maintain stability by sourcing the data from other drives without dropping the drive.
Vibration resistance becomes an important consideration when multiple drives operate in close proximity. Drives like Seagate IronWolf, WD Red Pro often include technology to reduce vibration effects, ensuring stability when multiple drives are working in parallel. Rotational Vibration sensors (accelerometers) are built into the hard drive to detect and compensate for vibration to protect it from the rotations of other hard drives and fans. Dual-Plane balance involves balancing the platters on two axes (horizontally and vertically) to minimize drive wobble during high-speed rotation and reduce the vibration transmitted to other drives in close proximity. Dynamic Fly Height (DFH) continuously adjusts the height of the read/write head based on vibration and temperature improving accuracy and reducing risk of data loss from misalignment caused by vibration. Servo Control allows the drive to make finer adjustments to head positioning, maintaining data integrity, often leveraging RV sensors to detect the vibration and adjust the head in real-time to keep the read/write process accurate. NoTouch Ramp Load ensures the head never touches the platter when not reading or writing data by parking the head away from the disk surface when idle. Enterprise-Class Vibration Resistance (ECVR) generally refers the inclusion of RV sensors, dual-plane balance, and additional dampening hardware.
Mean Time Between Failures (MTBF) and endurance ratings indicate the reliability and lifespan of a hard drive. It’s a calculation of the total hours a large number of drives operate under specific conditions and dividing it by the number of expected failures during that period. It’s expressed in hours and represents the average amount of operational time a device is expected to function without encountering a critical failure.
Annualized Failure Rate (AFR) estimates the likelihood that a drive will fail within a year and assists in planning drive replacements.
The cache size can affect its performance in tasks that involve random access patterns such as those in ZFS storage pools. Larger cache sizes improve read/write performance allowing more data to be temporarily stored for fast retrieval. Drives with larger caches (128 MB+) are recommended for NAS ZFS systems.
Power loss protection prevents data loss or corruption in case of unexpected power failures. ZFS is sensitive to corruption due to its reliance on transactional writes and checksum mechanisms to ensure integrity and maintaining the health of the pool.
Hard drives filled with helium improve efficiency, durability, and performance. It’s seven times less dense than air and helps reduce drag due to airflow resistance on the disks pinning at high speeds. This reduces the drives power consumption, heat, vibrations, and wear on components. More platters can fit within the drive due to the reduced friction, and increases storage capacity. These drives are ore expensive due to the complex manufacturing process.
Summary
Hard drives designed for NAS, Surveillance, and Data Center environments are ideal for 24/7 operation. Features like vibration resistance, TLER, and high MTBF are crucial for reliable performance. CMR technology is preferred over SMR for better write performance, especially in ZFS-based NAS systems.
