Can a Hard Drive Handle Streaming High Bitrate Movies?
I am always reading through Plex forums and Reddit posts both for information and to see the pain points others are having with their Plex servers. I find that many questions are related to what hardware would work best for a Plex server.
Some of the most common hardware questions are related to what CPU to choose, other common questions are related to storage, and whether solid-state drives (SSD) should be used instead of hard disk drives (HDD).
I decided to visit this topic as I find it is important to understand how choosing one drive over another when building a Plex server will impact streaming your media.
Media bitrates
For the purposes of this post, I will focus on streaming video files from a Plex server, such as movies, TV shows, or even family videos. This type of media usually makes up the bulk of what people stream from their servers and requires the most storage, processor, and bandwidth to stream to client devices.
All movie files on a Plex server will display a metric called bitrate. Bitrate is the amount of data that is encoded for a unit of time. In the case of streaming media, it is usually referenced in megabits per second (Mbps or Mb/s).
Bitrate matters for several reasons:
- Some older clients may not be able to handle media over a specific bitrate. For example, a Roku 3 may not be able to stream media if it is over 20 Mbps.
- Higher bitrate media files will need more storage space for the same media at a lower bitrate.
- When streaming over a network, or from a remote location, the connection speed will need to be at least the same or higher than the media file bitrate.
- The storage drive where the media file is located will need to be able to read the file at the same or higher bitrate.
While I listed multiple points above, when it comes to storage drives, the last point is important. I mentioned the others as something for you to think about with high-bitrate movies.
It is hard to find concrete bitrate values for different types of movies. There are too many movies to consider and then there are different resolutions - 480p, 720p 1080p, 4K - that make finding a specific bitrate to use difficult.
Instead, I decided to use the extremely high values for both Full HD (1080p) and Ultra HD (4K) movies as those would be the worst-case scenario.
The numbers I will be using are:
| Resolution | Bitrate |
|---|---|
| 1080p | 40 Mbps |
| 4K | 100 Mbps |
The table above lists some values you may find in remuxes of movies. These are movie files that have been ripped directly from the source disc and haven't been altered. They are as high-quality as you can get.
In reality, however, you would transcode them to a much smaller file size with a much lower bitrate. But for the sake of this post, I will look at the high bitrates.
Hard drive transfer rates
Let's park the talk of bitrates for a moment and switch gears to discuss hard drives. One common question about Plex storage is whether hard drives are good for streaming media files. Are they able to handle 4K movies?
All new computers today include SSD storage for the main storage. The operating system, applications, and games are stored on SSD drives as they provide much faster transfer rates than hard drives.
The one thing hard drives have over SSD storage is size. At the time of this post, you can get hard drives over 20TB in size that are affordable to consumers, while large-capacity SSDs are too expensive for the average consumer.
Larger hard drives make it easier for a Plex server owner to store a lot more media than smaller, faster, SSD storage.
Are hard drives fast enough since they are slower?
The transfer rate of a hard drive is measured in megabytes per second (MBps). You will notice the upper-case 'B' in the abbreviation that denotes megabytes.
The transfer speed of a hard drive is not constant for all data stored on the hard drive. The platter of a hard drive spins at a fixed RPM, so the angular velocity is constant. This means that data stored on the outer edges of the platter will be faster than data on the inner edges.
There are variables that determine the speed of transfer from a hard drive, which I won't get into here.
For my examples on hard drive transfer rate, I will use two numbers that will represent the fastest and slowest transfer rate of a spinning hard drive:
| Name | Transfer Rate |
|---|---|
| Minimum | 30 MBps |
| Maximum | 130 MBps |
These numbers are from an almost 8-year hard drive that is currently connected to my Plex server. It is a 3TB Western Digital Green drive that has been relegated to a scratch disk. It used to be one of the main drives for my server.
I am using the slowest drive I own as I will once again be taking the slowest speeds to compare to my example high-bitrate movie examples above for comparison.
Can a hard drive be used for streaming high-bitrate movies?
Now that all the talk about bitrates and hard drives is out of the way, let's have a look at the numbers.
As I mentioned earlier, the hard drive where the media files are located needs to be able to at least transfer the media file at the bitrate of the media.
In my examples, I am assuming that the Plex server is direct playing the movie and not transcoding. Transcoding will add additional overhead that could affect the speed of the streaming.
The one thing we need to keep in mind is that media bitrate and hard drive transfer speeds can't be compared directly. Bitrates are referenced in megabits per second while hard drive speeds are measured in megabytes per second.
We will need to convert one number to match the other. I will convert both to megabits per second so we can determine if a hard drive is fast enough to stream high-quality movies. To do that I will multiply the hard drive transfer speed values by 8 to get the bit value (8 bits = 1 byte).
The table below uses the bitrates and hard drive speeds as megabits per second using the values shown earlier.
| Mbps | MBps | |
|---|---|---|
| 1080p | 40 | 5 |
| 4K | 100 | 12.5 |
| HDD Minimum | 240 | 30 |
| HDD Maximum | 1,040 | 130 |
As you can see in the table above, my 8-year-old 3TB hard drive can manage a transfer rate of 240 Mbps to 1,040 Mbps transfer rate. This means it can easily stream a 4K movie that has been ripped directly from the disc. Multiple high-quality HD or 4K movies can stream from this hard drive at one time.
Newer hard drives or high-end enterprise hard drives would have even faster transfer speeds. I have seen my two mirrored 8TB Western Digital Gold hard drives reach 400 MBps (3200 Mbps).
What about solid-state drives?
If hard drives can be used for streaming, will a Plex server benefit from an SSD? Of course.
While hard drives are good for storing media files, SSD drives are much better for storing the operating system, the Plex Media Server application, and the Plex data directory.
The reason is that when a client connects to the Plex server, Plex will send down information about the media available on the server. This includes not only metadata but thumbnails, as well.
Having this information on an SSD will ensure information about media that is sent to the client will be sent as quickly as possible. This means that the responsiveness on the client side will be much better as the client is not waiting for the data to be read from a slower hard drive.
As a side note, it is also important to remember to backup your Plex data. Always try to use the 3-2-1 backup strategy: 3 copies of your data, on 2 different media with one copy being offsite. I highly recommend Backblaze for offsite. I have been using Backblaze for my backup for over 10 years and currently have 2TB backed up with them.
To summarize how you should manage storage on your Plex server:
- Media: Hard drives for their larger capacity and lower cost per terabyte.
- Plex application and data: SSD for the faster transfer speed.
In the end, though, it is your Plex server, and you can use whatever drives you prefer for both your media and Plex metadata. I hope this post has provided you with more information on what drives you can use for streaming your media.
