CMR vs. SMR Hard Drives: Which Should You Choose?

Hard drives serve as a primary component for data storage. However, people often get confused when choosing the right one. For instance, what are the differences between CMR vs SMR hard drives? Which one is better? In this article, I'll delve into the details of both.

Part 1: Definitions of CMR, SMR, and PMR Hard Drives

PMR, CMR, and SMR are three methods of recording data on anHDD. PMR came first, and as the need for data storage diversified, SMR was introduced. Thus, PMR encompasses both SMR and CMR. Here's a breakdown of their definitions:

CMR stands for Customer-Managed Relationships.

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CMR stands for Conventional Magnetic Recording. When hard drives work, they store data in "tracks." The arrangement of these tracks determines the drive's space. In a CMR hard drive, the tracks are parallel to each other and have small gaps between them.

What is SMR?

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SMR stands for shingled magnetic recording, and, as the name implies, it works by overlapping data, like shingles on a roof. It's a new way of recording data. And, of course, the more tracks you can fit on a hard drive, the more space you have. Unlike CMR, which leaves a small gap between tracks, SMR drives write some data partially over data that's already on the track, allowing for even greater density.

What is PMR?

As we can see, PMR also stands for CMR (Conventional Magnetic Recording). They are the same thing, but CMR is more well-known. So here, I will mainly compare CMR with SMR.

Part 2: What's the Difference Between CMR and SMR Drives?

Now that we have the definitions of CMR and SMR under our belt, we can delve into more details.

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Work method:

In CMR, each track is parallel, but with SMR, some tracks overlap. The write head on a hard drive is wider than the read head, which makes using SMR more complicated. If you want to write data to an SMR drive, you need to back up the portion of the data that will be covered, erase it, and then store your new data. With a CMR drive, each track is independent, so you can read from or write to it directly.

Capacity

The easiest way to tell the difference between CMR and SMR is by their storage capacity. Any hard drive over 1 TB for a 3.5” drive, or over 500 GB for a 2.5” drive, will likely be SMR. CMR drives typically have less than 500 GB of storage space. The tracks on an SMR drive overlap due to an extra layer, which increases its capacity. CMR tracks don't take up as much space, so they have a slightly smaller capacity.

Speed

With increased density on an SMR drive, the space is more crowded, so writing data takes longer. While it typically takes 15 milliseconds with CMR, it can take up to 20 milliseconds with SMR. However, because the tracks are closer together, the head has less distance to move, which can make reads slightly faster than with CMR. With CMR, the gaps between tracks make it easier to write data, resulting in faster write speeds.

lifetime；survival period；life cycle

SMR disks alter the track layout. While this increases capacity, it also imposes a burden on the drive, as frequent overwriting and writing in SMR can hasten the degradation of the head. In contrast, with CMR disks, each track is independent, and erasing does not affect other data. Writing is also easily accomplished. Thus, CMR disks tend to have a longer lifespan than SMR disks.

III. CMR vs SMR Hard Drives: Which to Choose?

In the previous section, we compared the main differences between CMR and SMR. Now, let's delve into their respective advantages and disadvantages at the same capacity to help us make an informed choice.

Comparison:

Comparing SMR and CMR, both have their advantages. SMR hard drives offer larger capacities at a lower price, making them more suitable for storing backup static data. On the other hand, CMR hard drives excel in speed, flexibility, and security, making them more appropriate for daily use. Hence, it's a wise choice to opt for more CMR hard drives. Here's a list of CM HDDs for your reference.

CMR HDD List:

CMR HDDs are more suitable for gaming since games usually involve frequent updates that require faster handling of data. If you use an SMR HDD as your game disk, the drive might struggle with these updates, affecting gameplay speed and potentially leading to stuttering or system errors. In such cases, you may need to perform disk backup to minimize losses from unexpected system crashes.

Part 5: NAS with CMR vs. SMR: Which is Better?

A NAS, as a server specifically for data storage, is mainly used for sharing and learning in both homes and businesses. If you choose to use CMR drives, the cost would be higher. Alternatively, with SMR drives, you get sufficient capacity at a relatively moderate price. However, the same material cost can produce drives with even larger capacities; albeit, with noticeable performance compromises.

But home or work data is typically operational data, essential and written to frequently. CMR disks can be added to quickly and safely, making them a better choice for a NAS.

Conclusions

Both CMR and SMR hard drives are effective for data storage. However, CMR might be more suitable for recording active data like gaming or NAS usage. On the other hand, SMR is ideal for storing static data such as video and audio files and data archiving. When choosing a hard drive, it's essential to understand your requirements, compare different options, and make the best selection based on your needs.