Know and understand solid-state media including memory cards (SD, xD, CFast)

3. Storage Devices and Media

Objective

Students will be able to:

• Identify the three main families of storage media (magnetic, optical, solid‑state) and describe their characteristic capacity ranges, costs, speeds and durability.
• Explain the advantages and disadvantages of each type of media.
• Compare the four principal solid‑state memory cards (SD, microSD, xD, CFast) and select the most appropriate card for a given device or task.
• Understand capacity categories, speed‑class markings and required file‑systems.
• Apply safe handling, backup and archival practices, and recognise emerging portable‑storage technologies.

1. Overview of Storage Media Types

Storage media are classified by the technology used to retain data.

• Magnetic media – data stored on magnetised particles on rotating platters (hard‑disk drives) or on linear tape.
• Optical media – data stored as pits and lands on a disc that is read by a laser.
• Solid‑state media – data stored in non‑volatile flash memory cells; no moving parts.

2. Comparative Summary of Media Types

3. Solid‑State Removable Memory Cards

3.1 Why Use Solid‑State Cards?

• No moving parts – excellent resistance to shock, vibration and temperature extremes.
• Low power consumption – ideal for battery‑operated devices.
• Fast random‑access times enable rapid start‑up and file transfer.
• Very compact – can be built into slim cameras, smartphones, drones and action cams.

3.2 Common Card Types

3.3 The SD Card Family – Capacity Classes & File Systems

• SD – up to 2 GB; formatted with FAT12 or FAT16.
• SDHC (High Capacity) – 2 GB – 32 GB; formatted with FAT32.
• SDXC (eXtended Capacity) – 32 GB – 2 TB; formatted with exFAT.

Choosing the correct file system is essential because each has partition‑size and file‑size limits:

• FAT12/16 – maximum partition 2 GB; virtually no file‑size limit for typical photos.
• FAT32 – maximum partition 2 TB, but individual files cannot exceed 4 GB.
• exFAT – removes the 4 GB file‑size ceiling; required for high‑resolution video files.

3.4 Speed Classes – Minimum Sustained Write Speed

3.5 xD‑Picture Card – Quick Reference

• Advantages: Small form‑factor for early compact cameras; proprietary interface reduced licensing costs.
• Disadvantages: Maximum capacity only 4 GB, slow write speeds (2‑6 MB/s), limited device support, now obsolete.

3.6 CFast Card – Quick Reference

• Advantages: SATA‑III (6 Gb/s) interface gives theoretical 600 MB/s; high capacity (up to 2 TB); excellent for 4K/8K video and high‑burst DSLR shooting.
• Disadvantages: Larger physical size; requires dedicated CFast slot; higher purchase price; not interchangeable with standard SD slots.

4. Choosing the Right Card

1. Device Compatibility – Check the manufacturer’s maximum supported type and capacity (e.g., many entry‑level cameras cap SDXC at 128 GB).
2. Capacity Required – Estimate using typical file sizes:
   • 12‑MP JPEG ≈ 5 MB per image.
   • 4K @ 30 fps ≈ 350 MB / min (≈ 21 GB / hour).
   • 8K @ 30 fps ≈ 1 GB / min (≈ 60 GB / hour).
3. Speed Class – Match the minimum write speed to the recording bitrate (e.g., V30 for 30 Mbps, V60 for 60 Mbps, V90 for 90 Mbps or higher).
4. Reliability & Warranty – Prefer cards with built‑in ECC, a manufacturer’s warranty of ≥ 2 years, and a proven track record (e.g., SanDisk, Lexar, Sony).
5. Environmental Factors – Ensure the card is rated for the operating temperature range of the device (‑25 °C to +85 °C is typical for professional cards).
6. Security Needs – For confidential footage consider cards that support hardware encryption or use write‑once (WORM) media for archival copies.

5. File‑System Implications

Each SD family level mandates a specific file system because of partition‑size limits:

• SD (≤ 2 GB) – FAT12/16; universally readable by cameras, computers and legacy devices.
• SDHC (2‑32 GB) – FAT32; supports larger partitions but cannot store files larger than 4 GB – a problem for long‑duration 4K/8K video.
• SDXC (≥ 32 GB) – exFAT; removes the 4 GB file‑size ceiling and is required for most modern high‑resolution video recordings. Some older devices need a firmware update or an external exFAT driver.

Formatting the card in the device it will be used in (rather than a PC) helps the device write the correct allocation tables and maintains optimal performance.

6. Data Safety, Backup & Archival Strategies

Although flash cards are non‑volatile, data loss can still occur.

• Physical damage – bending, crushing, water ingress, or exposure to extreme heat.
• Electrical issues – electrostatic discharge or sudden power loss during a write operation.
• File‑system corruption – improper ejection, interrupted formatting, or virus infection.

Best practice for preserving data:

1. Always use the operating system’s “Safely Remove Hardware” / “Eject” command before disconnecting.
2. Back up critical files immediately after a shoot:
   • Copy to a computer’s internal drive or an external HDD/SSD.
   • Maintain a second copy on a different medium (e.g., magnetic tape or cloud storage) for redundancy.
3. Store unused cards in anti‑static sleeves, in a dry, temperature‑controlled environment (15 °C – 25 °C, < 60 % RH).
4. Periodically re‑format the card in the device it will be used in to refresh the wear‑leveling algorithm.
5. For long‑term archiving (> 10 years) consider migrating the data to magnetic tape (LTO) or a high‑quality optical disc, as flash cells lose charge over time.

7. Environmental & Security Considerations

• Temperature & Humidity – Most cards operate between –25 °C and +85 °C; prolonged exposure to high humidity can cause corrosion of contacts.
• Static Electricity – Handle cards by the edges and avoid touching the gold contacts.
• Data Encryption – Some high‑end cards (e.g., certain CFast models) offer hardware AES‑256 encryption for confidential footage.
• Write‑Once (WORM) Media – For legal or forensic purposes, a write‑once card guarantees that data cannot be altered after recording.

8. Emerging Portable‑Storage Technologies

While the syllabus focuses on SD‑family cards, it is useful to be aware of newer solutions that are beginning to appear in professional workflows:

• CFexpress – Uses PCIe 3.0/4.0 interface; theoretical speeds up to 2 GB/s, already adopted in high‑end cinema cameras.
• NVMe‑based Portable SSDs – Enclosed in rugged USB‑C or Thunderbolt casings; offer SSD‑class performance (≥ 1 GB/s) with removable form‑factor.
• Hybrid Memory Cards – Combine a small amount of high‑speed DRAM cache with NAND flash to improve burst write performance (e.g., “UHS‑III + DRAM” cards).

These technologies illustrate the trend toward ever‑higher data rates required for 8K/10K video and high‑resolution still‑image capture.

9. Summary

• Storage media fall into three families – magnetic, optical and solid‑state – each with distinct capacity, cost, speed and durability profiles.
• Solid‑state removable cards (SD, microSD, xD, CFast) provide fast access, shock resistance and compactness; SD cards dominate the consumer market, while CFast serves professional video and high‑burst photography.
• Card selection must consider device compatibility, required capacity, speed class (including V90 for ≥ 90 Mbps video), reliability, environmental rating and any security needs.
• Correct file‑system formatting (FAT12/16, FAT32, exFAT) prevents issues such as the 4 GB file‑size limit on FAT32.
• Data safety relies on safe ejection, regular backups, proper storage conditions, and, for long‑term archiving, migration to magnetic tape or high‑quality optical media.
• Emerging formats such as CFexpress and NVMe portable SSDs are expanding the performance envelope beyond traditional memory cards.