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Selecting the Right Hard Drive for Your Needs

There are more hard drives to select from than ever before from several mainstream hard drive manufacturers. This can get very confusing for the average professional, consumer or prosumer. What features are desirable in a hard drive? That depends largely on the application, available connections on the host computers, how the drive will be used, and perhaps environmental factors (e.g., anticipated shock/ vibration). The two main categories of hard drives are internal and external. Internal drives are installed inside a computer or drive array while an external drive is a free standing device with a solid protective cover used outside a computer, typically sitting on a desk next to the computer.  

Back Up/ Archive – One of the issues in data storage is back up vs. archive.   A backup is a linear copy of all of a set of information from start to finish, such as all of the content of a storage volume.   Restoring a backup requires restoring all of the content in the same linear fashion.   The two differences with archive are the random access ability to quickly restore only a particular file or clip, while the second is its permanent nature using long term storage formats such as LTO (linear tape open) or ODA (optical disc archive).   With moving parts that can fail over time, hard drives are unsuitable for the long term archive of media. If multiple copies of media are stored on the same or different hard drives, then hard drives can be suitable for backup copies. Best practices in many organizations is to create archive media immediately after content is produced, while others use simpler hard drives through some or all of the production process. See archive-systems-and-lto-media for more details.   The eMAM™ system from Empress Media Asset Management helps many organizations manage their archive system.

Drive Capacity – Nowadays drive capacity is typically measured in gigabytes (GB) or terabytes (TB). More storage is needed for high bandwidth data such as with HD/UHD-4K, 8K video. For still photos, a 1 TB drive will contain tens of thousands of digital images. In the 21st century, the vast majority of storage capacity and bandwidth is consumed by video content.

For HD 1080p video content, to estimate how much storage is needed: Add up the total amount of raw footage you intend to shoot, in hours and multiply by 13 to get the number of gigabytes required.  

For HD 720 format--a slightly lower resolution—the factor is 11 GB/hour.   For example, 6.6 hours of HD 1080 footage would use about 85.8GB of storage. Allowing for extra storage will increase drive performance, because a nearly full drive is much less efficient. There are many factors that affect bandwidth and storage requirements for video content: frame rate, color sampling (4:4:4, 4:2:2, etc.), number of audio channels, audio sampling rate, number of bits (12/10/8 bit depth), frame size, resolution, motion of content, etc. Higher quality video settings require more storage.

A review of storage capacity units:

1000 Bytes

1 kilobyte (a very small file, such as a notepad file)

1000 kilobytes             

1 megabyte (still not considered a large file – on the order of a digital photo). A small floppy disk may contain 1.4 MB.   A CD-R may contain 700MB of content.

1000 megabytes         

1 gigabyte (an HD clip of several minutes with highest quality settings).   A DVD may contain 4.7GB of content, while a Blu-ray may 25GB (single layer) or 50GB (double layer).

1000 gigabytes            

1 terabyte (an HD movie, multiple TB for an UHD movie). Hard drives usually hold about 1TB.  

1000 terabytes

1 petabyte (larger enterprises typically have data stored in the multiple petabyte range).   Large storage or archive systems are required to store petabytes of data.

789 petabytes of data traverses the internet worldwide or enough to fill 168 million DVDs (source: Mashable, 2012 statistics).

RPM – Typically 5,400, 7,200 or in some cases 10,000 RPM. Of course the faster the RPM, the faster data will transfer to/from the drive. The tradeoff is that faster drives will consume more power and perhaps will not last as long due to faster spindle wear. For most applications 5400-7200 RPM are fine.

SSD vs. Conventional Hard Drives - To spin or not to spin, that is the question. For most applications spinning hard drives offer the best value, while solid state drives (SSDs) offer several advantages and decline in price over time. SSDs use rugged flash chips that are more durable and shock resistant, are faster, require less power, run cooler, are noiseless, and can be made smaller.   Traditional spinning hard drives are cheaper and come in larger capacities, but they can fail due to the moving parts: spinning platters, delicate read/write heads, and a motor.  

External Hard Drives
External hard drives usually have a hard external case to protect as they sit on a desk.   They are self-contained units with several different options.

Connectivity:   Usually on the back of the unit, and sometimes on the front of the external hard drive there is one or more available connections to connect to a computer, camera, or other device.   In increasing order of connection speed, common connections are Firewire 400/800, USB 2.0/3.0, eSATA, Thunderbolt, and Thunderbolt 2.   The connections are generally incompatible, so a user must have appropriate hard drive slots to match the available computer slots and cables.  Selecting the fastest available port will reduce transfer times,   especially important when individual video files can be 1TB or larger.  

Many external drives have multiple connections, sometimes referred to as “triple” or “quad” in their descriptions, which will typically include a combination of Firewire 400/800, USB, and eSATA. Thunderbolt drives usually only have Thunderbolt ports exclusively, sometimes “dual” Thunderbolt/2, plus perhaps one other port type (such as USB 3.0). Below is a speed comparison chart for the various ports typically available on hard drives expressed in Mbits/s (megabits per second) and also MB/s (megabytes per second) – 1 byte equals 8 bits of data. Sometimes it is easier to comprehend bytes rather than bits per second since file sizes are expressed in bytes (kilobytes, megabytes, gigabytes, and terabytes).


RAID Drives – RAID (Redundant Array Independent Drives) protect content by copying content to two or more drives in a combined unit.   If a part or an entire drive fails, then the content will be available from another drive.   RAID drives support one or more options for RAID storage.   Although RAID 0 only optimizes storage across the multiple drives for better performance, RAID 1 and all higher levels offer some level of protection when all of the data is written to two or more discs.   RAID systems cost more and lose some of the available storage to redundant copies. Because a controller error of (a very unlikely) simultaneous failure of multiple discs could result in data loss, archive systems are still the best option for permanent archive.  

Power Options – External power drives can have a separate power adaptor or may be bus powered through the cable connecting to the computer. Some drive manufacturers have elected to integrate the power supply into the drive enclosure, so there is just an AC power cord to connect without any “wall warts”. This eliminates the need to pack a separate power adapter (which may get lost or misplaced) in mobile field applications. Bus powered drives have definite advantages in mobile applications, but may have slower RPM due to limited power available from the computers port connection. For studio applications, a separate power unit or integrated power supply offers better performance results.

Mobile vs. Studio Drives – External drives may be designed for field/mobile use, or mainly for indoor studio use. Typically, mobile drives are bus powered, more compact, have lower RPM, or are SSD based. Many mobile drives have ruggedized features such as protective rubber bumpers, and may offer some water resistance. SSDs offer the best protective features, because they are virtually immune to shock. Studio/desktop drives are typically larger, heavier, have RAID options, separate power supplies, and larger capacities. Of course, studio drives may be used in the field.

Hybrid Drives – Some manufacturers have begun producing hybrid drives (for both internal and external applications). Hybrid drives have both a spinning hard drive paired with a small internal SSD. The SSD acts as a buffer or cache for the spinning hard drive, thereby improving the overall performance dramatically over a spinning drive alone, while keeping costs reasonable. There are none of the other SSD advantages such as lower power or immunity from shock/vibration since the spinning drive is still there. Hybrid drives are perfect for studio applications. Note that all hard drives, even those without SSD, have some internal solid state memory cache or buffer to improve performance, but it is usually much smaller than that offered by SSD hybrid drives (typically 64 to 128 MB). Larger buffers or cache memory are more desirable of course.

Internal Hard Drives

Internal hard drives are designed to be used inside a larger device such as a laptop, desktop computer or drive array – they are bare drives without any protective enclosures. The selected drive must be compatible with the device in which it is installed. The specifications or data sheet for the host device must be consulted to check compatibility. Some manufacturers of RAID towers require the use of their own drives, while others may use any type of compatible drives (aka JBOD or “just a bunch of drives” often referring to drives in a RAID array of mixed type rather than uniform type). Internal drives generally have connections for SATA.  

Some of the same considerations for external drives apply to internal drives as well – speed (RPM), capacity, SSD vs. spinning. Internal hard drives may be used inside of RAID drive housings, so the effective storage capacity must be calculated in the case of a RAID unit to account for stripping/ mirroring overhead.

For laptop computers, 2.5 inch drives are usually required, but for desktop applications may be as large as 3.5 inches. So important characteristics for internal drives are: capacity, RPM, cache size (larger better), physical footprint (2.5 vs. 3.5), SATA II vs SATA III, hybrid or not, RAID application, short stroke (used in certain enterprise applications) and SSD/spinning disk.