LTO Drives: Full-Height (FH) vs Half-Height (HH) ?

At MagStor, we get asked all the time what's the difference between Full-Height and Half-Height drives?

Here's a breakdown:

1. Physical Size:

  • Full-Height (FH): These drives are typically 2U (two rack units) high when mounted in a server rack. They are physically larger, taking up more vertical space.

     

  • Half-Height (HH): These drives are 1U (one rack unit) high, meaning they are half the height of full-height drives. This smaller form factor allows for more drives to be installed in a given rack space.

     

2. Performance: This is often the most significant practical difference, especially in more recent LTO generations (LTO-8, LTO-9, LTO-10).

  • Higher Native Transfer Speeds: Full-height drives generally offer higher native (uncompressed) data transfer speeds than half-height drives of the same LTO generation. For example, an LTO-9 FH drive might achieve 400 MB/s, while an LTO-9 HH drive might be 300 MB/s. This difference translates to faster backups and restores, which can be critical for large datasets or tight backup windows.

     

  • Faster Seek and Repositioning: FH drives typically have larger, more powerful motors. This allows for quicker acceleration and deceleration of the tape, leading to faster seek times (locating specific data on the tape) and reduced "backhitching." Backhitching occurs when the host system can't feed data to the drive fast enough, causing the drive to stop, rewind a bit, and then restart. More powerful motors and larger data buffers in FH drives reduce the frequency and duration of these backhitches, improving overall throughput and reducing wear.

3. Durability and Duty Cycle:

  • Load/Unload Cycles: Full-height drives are often designed for significantly higher numbers of load/unload cycles. This refers to how many times a tape cartridge can be inserted and ejected from the drive before the loading mechanism might experience wear. FH drives are often rated for hundreds of thousands of cycles, making them ideal for high-volume automated tape libraries where tapes are constantly being loaded and unloaded. Half-height drives, while still very durable, typically have lower load/unload ratings (e.g., 80,000 cycles).

  • Robust Mechanics: Historically, and to some extent still true, FH drives could incorporate larger, more robust mechanical components in the tape path, contributing to overall durability. This was particularly true in earlier LTO generations. While modern HH drives are incredibly advanced, the larger footprint of FH still allows for potentially more robust designs for continuous, demanding operation.

  • Cooling: The larger physical space in FH drives can sometimes allow for better internal airflow and cooling, which can contribute to the longevity of internal components.

     

4. Target Use Cases:

  • Full-Height Drives: Often preferred for:

    • Enterprise data centers

    • Large automated tape libraries

    • Environments with extremely high data volumes or very strict backup/restore time requirements

    • Applications demanding the absolute highest performance and longest operational life.

  • Half-Height Drives: More commonly found in:

    • Desktop standalone units 

    • Smaller server environments

    • Entry-level to mid-range tape libraries

    • Environments where space is a premium.

In summary:

While both FH and HH LTO drives adhere to the LTO standard and offer excellent reliability for long-term data archiving, full-height drives generally provide higher performance (faster transfer speeds, quicker seek times) and are built for more demanding, high-duty cycle environments with a greater tolerance for frequent tape changes. Half-height drives offer a more compact and often more cost-effective solution for many users without compromising the core benefits of LTO technology (capacity, longevity).

Still unsure?  Contact MagStor today for a free consultation.