This article explains some of the major differences among the various HDD classes, and offers suggestions on what to consider when choosing an HDD for your Synology servers.

• Make sure refer to the Synology Products Compatibility List to ensure system stability if third-party products are used with your Synology servers.¹
• Four main HDD classes are currently available on the market, with each designed for specific applications, workloads, mean time between failures (MTBF), and power-on-hours (POH). HDDs of almost all classes can be installed used for your Synology servers, however, we recommend choosing the most suitable ones for optimal system stability and performance.

Term Explanation:

• Mean time between failures (MTBF): MTBF is a statistic used by manufacturers to state the HDD reliability. A high MTBF usually indicates a low chance of HDD failure. Please note that no HDD manufacturers can guarantee zero failure.
• Power-on-hours (POH): POH is the length of time, in hours, that electrical power is applied to a device. The following two categories are usually used for the POH of HDDs:
  • 8/5: 8 hours a day, 5 days a week.
  • 24/7: 24 hours a day, for every single day of the year.
• Workload: The amount of data (TB) transferred via a single HDD per year.

Enterprise HDD

• An enterprise HDD is generally manufactured using more advanced technology and superior components to provide better performance, POH, MTBF, vibration protection, and error correction.
• These HDDs are suitable for environments requiring high data availability and consistent throughput even when huge amounts of data are being transferred.
• Enterprise HDDs are suitable for businesses with many employees accessing files, database servers, or virtual storage systems simultaneously.

NAS HDD

• A NAS HDD is specifically designed for NAS usage and often features better durability, balanced performance, and lower power consumption when compared to a desktop HDD. These HDDs are a more affordable option compared to enterprise HDDs.
• Some NAS HDDs do not come with vibration sensors and may not be suitable for Synology’s multi-bay or rackmount models. Make sure to check with the HDD manufacturers for detailed HDD specifications before purchase.

Surveillance HDD

• Designed to fulfill the 24/7 demands of long video recordings, surveillance HDDs are optimized for sequential write-operations, but offer lower random-access performance.
• Some surveillance HDDs do not come with vibration sensors and may not be suitable for Synology’s multi-bay or rackmount models. Make sure to check with the HDD manufacturers for detailed HDD specifications before purchase.
• We recommend using enterprise HDDs if the workloads of your Synology servers exceed the maximum capacity of surveillance HDDs.

Desktop HDD

• A desktop HDD is designed for desktop or laptop computers, which usually requires the installation of a single HDD.
• Most desktop HDDs are more affordable, but seldom come with vibration protection. The lack of vibration protection makes the HDDs more vulnerable in RAID environments, since vibration from the system chassis and other HDDs may affect the system performance and the HDD health status. Therefore, we do not recommend installing desktop HDDs on your Synology servers.²