Dissecting a Hard Disk: What I Learned by Taking One Apart

SEAGATE HARD DISK

Recently I came across this old harddisk when searching for a ball in the cupboard. So my curiosity dives me into exploring the harddisk.

Now I started dismantling the harddisk to see what is inside. I have an Electron screwdriver set which I used to unscrew it.

Screwdriver set

Capacity

To know how much capacity that the harddisk is, you need to know these things to check.

1. Look for the label first

Most hard disks have a label on it which mentions the following:

• Storage capacity
• Model number
• Brand

2. Check the model number

The label does not mention any storage capacity. So I look for a model number. The model number ST340015A breaks down like this:

• ST = Seagate Technology
• 40 = 40 GB
• 015A = Family or series identifier

This says it is an old hard disk like the mid 2000’s used by Windows XP.

Dismantling Process

1. Controller board

I have four screws on it. I unscrewed it and took the board apart.

HDD Controller board

This Control board controls data flow between the disk and computer. It is responsible for managing read/write operations.

It Contains:

• Main controller chip (like a mini CPU)
• Cache (buffer) chip
• Connectors

HDD Connectors

• Power management
• Firmware (stored in ROM chip)

Think of it as the hard disk’s motherboard.

2. Inside part of HDD

To the backside of the controller board, there were 5 screws under the label (Common trick by manufacturer).

Removing all screws and opening the metal plate.

Inside HDD

Disclaimer: You should not open it in normal room air unless you’re just exploring out of curiosity. I do it because it is old.

It contains,

1. Platter: Stores all data magnetically.
2. Spindle Motor: Spins the platters at high speed.
3. Read/Write Head: Reads from and writes data to the platter surface.

4. Actuator Arm: Moves the read/write head across the platter.

5. Voice Coil Actuator: Controls the movement of the actuator arm precisely.

Why Less Capacity + Heavy weight while smartphone comes with more capacity in less weight

🧠 1. Technology Has Advanced Drastically

HDD vs Mobile phones

It’s likely from the early 2000s. At that time, 40 GB was considered a lot — Windows XP could run on 2 GB of space.

Storage density (amount of data that can be stored per square inch) was very low back then.

2. Mechanical Design = Bigger Size

It uses spinning magnetic platters, motors, and mechanical arms to read/write data.

This design makes it heavy and bulky. In contrast, your phone uses flash memory which:

• Has no moving parts
• Is much smaller
• Is faster and lighter

💰 3. Cost per GB Has Dropped Massively

Year Cost per GB (approx) Storage Typically,

• 2002 has ₹400–₹800 per GB .
• 2025 has ₹0.50–₹2 per GB 128 GB+ in phones.

Old hard disks are like a vintage ambassador car — huge, heavy, and outdated compared to today’s sleek electric vehicles (your phone’s storage).

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