Hard drives come in many storage capacities, sizes, and speeds. There are many brands to choose from and there are various features and specifications to choose from.
As SSDs have taken over both consumer and enterprise storage markets, hard drives have a very low relevance as the primary storage drives. However, people still use hard drives for various purposes. The biggest benefit of hard drives is their cheapest price per GB. For the same storage space in a hard drive, you may have to pay 2x or 3x more for solid-state drives. High-performance drives may cost you even more than that.
So, if you want to choose a hard drive for any purpose, here is a detailed buying guide for you. I have already published a buying guide for SSDs which you can check here.
1. Form Factor
There are two types of hard drive form factors in the consumer market. One is 2.5″ and the other one is 3.5″. The 3.5″ is a standard size for desktop computers and external drives. In this form factor, you get higher storage capacity because a single hard drive could have more than one magnetic platter. Also, the size of the platter is going to be big compared to the 2.5″.
The 2.5″ is a standard hard drive size for laptops and compact external hard drives. These are lighter in weight, portable, and often come in smaller storage capacities. The same form factor is utilized by the 2.5″ SSDs as well.
So, if you are buying a hard drive for your laptop to install internally, you generally get an option of 2.5″. However, for desktops, you can choose between 3.5″ and 2.5″ drives. Bigger form factors generally come with more noise, better performance, higher price, and more storage space.
2. Capacity
The best thing about the hard drives is that they come in huge capacities. You can easily get a 10TB or a 20TB hard drive. Although it depends on your specific requirements, you always have the advantage of having a single drive with multiple TB of data. 500GB to 1TB is the perfect storage space for basic storage needs like documents, photos, etc. 2TB to 4TB drives are suitable for storing large media files, games, etc. 6TB to 10TB or higher storage variants are more suitable for extensive storage like video files, databases, or NAS.
Lower storage capacity drives are generally more power-efficient, silent, and cheaper. On the other hand, the higher storage variants give you enough space and peace of mind for future upgrades. There is nothing special you get with the different storage capacities.
Unlike SSDs, you get no special benefits with higher variants such as higher TBW or better performance. It is just your storage space requirements and the budgets that decide which capacity you want to pick. If you are going for the higher storage capacity, you just pay more and get nothing extra except the space.
3. RPM (Rotations Per Minute)
Hard drives store the data on magnetic platters. The bits are stored in the form of magnetic charge where a difference in charge represents a bit. So, the data storage and retrieval mechanism stays stationary (the read/write head moves in set directions). To access any data block, the disks have to spin at a certain speed. A higher RPM generally means better read/performance and vice-versa. You get three RPM options when choosing a hard drive.
5,400 RPM
This is the slowest hard drive speed and is generally found in the smaller 2.5″ drives. The typical sequential read/write speed ranges between 80 to 100 MB/s. These drives are quiet, energy efficient, and suitable where high-speed data access is not required.
7,200 RPM
These hard drives provide the best balance of price and performance. They come with comparatively better performance but higher price tags. The typical sequential speed ranges between 100 to 150 MB/s. They come in both 2.5″ and 3.5″ form factors so you can use them in almost any system.
10,000 RPM
There are much faster drives intended for high-performance systems and even workstations. However, they are expensive and SSDs are competing pretty well with these. However, you can still get one for you and you can get an advantage of high-storage space for sure.
15,000 RPM
These drives are made for enterprise environments, servers, and other performance-critical environments. The typical sequential read/write performance ranges between 200 to 300 MB/s. These drives are pretty rare because they are almost replaced by the solid state drives.
So, all in all, you get two main RPM options i.e. 5400 RPM and 7200 RPM. 7200 RPM offers better performance but a little higher price tag. 5400 RPM is for basic tasks where performance isn’t an important matter.
It is important to note that whatever RPM a hard drive can achieve, it is impossible for them to go beyond 600MB/s in the consumer environment because of the SATA-3 limitations. You can use some kind of caching for external drives and reach more than 600MB/s but that is a topic for another day.
4. Cache Size
A cache is a small amount of buffer installed in your hard drive that serves as a high-speed memory. Its basic task is to store the frequently accessed data by the operating system. Because hard drives have a pretty bad random performance, this cache reduces the storage bottleneck during CPU operations.
The drive’s controller predicts the data that will be required by the system soon. So, it finds it and stores it in this cache. This basically helps with the access of small files. These are the files that are generally utilized by the software and games that we run on our computers. It also reduces the latency and shows improvements during heavy workloads.
Small Cache (16MB – 32MB)
This amount of cache is enough if your hard drive’s primary purpose is going to be raw data storage. Modern software requires much more than this amount of cache to work effectively. So, this small cache is good for basic tasks such as web browsing, file storage, and light application usage.
Moderate Cache (64MB – 128MB)
This can be considered a pretty enough cache for light to average usage. You can consider using this drive as the primary OS drive if your workloads are low. This cache can serve you pretty well if you want to do web browsing, file storage, light gaming, and some kind of other application usage.
Large Cache (128MB+)
I would recommend going for the higher amount of cache you can get. Having more of it would help you play games and do other demanding tasks on your computer. You can even do video editing and multitasking.
Again, you can’t compare this cache’s performance with SSD’s cache performance. This is because the CPU and RAMs are coming with huge read/write speeds. The hard drives can’t really catch up with that. But, they are still good with the old systems if you can get enough cache for your software to operate.
5. Interface
For personal computers, you get the option to choose just the SATA drives in case of internal drives. You can still get external hard drives and run them through USB but we are talking only about the internal drives.
SATA-3 is the top and most common interface for the hard drives. Again, the maximum practical speed is limited to 600 MB/s. However, all the SATA variants are forward and backward-compatible. But, you will hardly find SATA-1 or 2 drives in 2025.
For enterprise hard drives, the most popular interface is the SAS. These are much more expensive drives and require specialized hardware which can be setup in enterprise environments.
6. Reliability and Durability
For hard drives, you can check and compare the load/unload cycles, power on hours per year, TB/year, and warranty period. These are the things that would determine your drive’s reliability. Some drives can also come with the MTBF (Mean Time Between Failure) numbers. It is good to go for above 1 Million hour MTBF drives.
7. Purpose-Specific Features
When looking for hard drives, you will see drives designed for specific purposes such as NAS drives, Surveillance drives, and enterprise drives. These drives are designed for these specific purposes and it is better not to use them for other tasks.
For example, the NAS drives are made to work 24 hours and priced at higher prices. You should not waste your money on this drive by installing it on your personal computer.
In the same way, the surveillance drive, the manufacturers design them for high write operations with better reliability. The enterprise drives are again made for higher reliability and performance. So, if you are choosing a hard drive for a specific purpose, make sure to get a hard drive that is made for that specific task.
8. Price vs. Performance vs. Usage
It is always good to look for the drives that offer the best value for your money. Hard drives aren’t very expensive. So, don’t go for those fancy features if you don’t really need them. There are performance drives that are going to cost you but checking that performance is enough for you. Modern systems are very fast and require very high data read/write speeds to work optimally.
For continuous operation drives, you’ll have to pay more because they are made for those tasks. Do not try to save money there because you may end up damaging your drive while it is working for 24 hours and data may be lost permanently.
Hard drives are now used mostly for raw data storage. So, if you plan to dump your data in it and keep it aside, it is better to go for drives with higher storage capacity to save space.
You will generally see drives marketed as high-performance drives but they may not be ideal to be used as the primary operating system drive in your computer. It is always better to use an SSD for that purpose. You can opt for a smaller size SSD and get a bigger hard drive for raw data storage.
9. Brand and Reviews
There are many brands in the market offering their hard drives in different capacities, speeds, and for various specific tasks as we discussed above. Make sure to go for a reputed brand and check reviews before you make your purchase.
10. Environmental Considerations
Lower-RPM drives tend to be quieter and more power-efficient. These are good for home and office environments. If your drive is going to be running 24/7, consider getting a drive with better energy efficiency. A big advantage of hard drives is that they don’t generate a lot of heat. But, still, if you are combining multiple drives for a database environment, RAID, or NAS, you may have to set up some sort of cooling mechanism as well.
In modern systems, hard drives are used for backup and raw data storage (typically to store big files) because of their cheap storage price. They offer bad performance compared to the SSDs but still, they are effective for bulk data storage. This might be the reason why they are still available in the consumer market.
With this buying guide, I hope you will be able to pick the best hard drive for your system.