Should I choose SSD or HDD for a large hard disk server? This question is no longer a simple "who is faster" answer. Especially when you are facing a large-capacity hard disk server, starting with tens of TB or even hundreds of TB, you can no longer just look at the read and write speed, but look at multiple dimensions such as scenarios, costs, durability, and power consumption.

　　What is a "large hard disk server"? Don't underestimate this definition. Only by clarifying the scope can we talk accurately. Large hard disk servers usually have a single hard disk capacity of ≥10TB, and some even have hundreds of TB; they are often used in scenarios such as file storage, archiving, media content hosting, and backup; the number of hard disks is ≥4, and even RAID arrays or distributed clusters are configured;

　　Misunderstanding reminder: SSD is not a product that completely replaces HDD

　　SSD and HDD are not completely competitors in essence, but complementary. Each has its own living space.

　　Which one should I choose for a large-capacity server? The scenario is the answer. There is no perfect hard disk, only hard disks suitable for the scenario.

　　Scenario 1: Website/database server (small data volume, high concurrency) full SSD is recommended

　　Reason: website database is frequently read and written, IOPS requirements are high; latency tolerance is low, users will not wait for you; database index and log writing pressure is high. Even if the total amount of data is not large, it is worth investing in speed.

　　Scenario 2: Archival storage/video files/log files (large data volume, low access frequency)

　　Recommendation: HDD or hybrid solution (SSD cache + HDD storage)

　　Reason: high write frequency, low read frequency; after a write, it will not move for a long time, the speed of SSD cannot be fully utilized; HDD has lower cost and is suitable for cold storage in "blocks".

　　Scenario 3: Virtualization platform/cloud service node (IO intensive + multi-tenant)

　　Recommendation: NVMe SSD or enterprise-level SATA SSD

　　Reason: multi-user concurrent read and write, high IOPS is the lifeline; "write amplification" is prone to occur, SSD life control must be good; HDD is a "negative example" in this scenario.

　　Scenario 4: Backup server/snapshot archiving/certificate storage platform

　　Recommendation: HDD main + SSD cache

　　Reason: write more and read less, data is not frequently accessed once written; cost-driven business, tens of TB SSD is not realistic; performance can be improved through hybrid architectures such as ZFS, bcache, LVM, etc.

　　When choosing a hard drive, you have to think like an architect, and don't be misled by the saying "SSD is faster". The server is not a desktop computer, and its storage selection should be comprehensively considered from the business characteristics, access mode, cost budget, reliability and maintainability. What you need to do is not to "choose the most expensive", but to choose the most suitable storage combination.