In addition to a nimble processor, plenty of RAM and a high-performance graphics card, a fast PC also needs a powerful hard drive. There are two types of hard disk storage to choose from: the HDD for large capacity requirements or the SSD for particularly fast data exchange. But how much storage space is actually needed?? And which type of hard disk is suitable for which tasks? HDD or SSD? Which memory is the right one?
Hard disk drive (HDD)
Hard disk drives are magnetic storage media in which data is written by the read/write head in concentric tracks on rotating disks. The coating of the disk surface is magnetized without contact and as a result of the remanence (remaining magnetization) the storage of the data succeeds.
Very large storage capacities available
Inexpensive to purchase
Recovery possible in case of data loss
Comparatively slow read and write speed
Less robust and hard-wearing due to moving parts
Solid State Disk (SSD)
Solid state disks have grown to a popular size in the end user market since 2007. SSDs are also colloquially referred to as hard disks, although strictly speaking they are not. They are flash memory devices on which storage is realized via semiconductors. Compared to HDDs, they have no moving parts and thus score with low noise and increased shock resistance. SSDs have the advantage of high sequential write and read speeds, with transfer rates of up to 4 GB/s.
Very fast transfer of data possible: sequential write and read speeds of up to 4 GB/s
Noiseless storage, as there are no mechanical components
Robust against shocks
Little chance of recovery in case of memory loss
Shorter lifetime, since the number of write and read processes is finite
What is stored where?
Since SSDs have been available, tuning operating software like Windows has taken a back seat. While in the past optimizations were made to reduce the boot time from five to three and a half minutes, today’s SSDs can boot in less than 20 seconds.
Here it becomes clear: Running the operating system on an HDD is not a good idea, unless there are no other slots for connecting an SSD.
Applications that have to be accessed frequently and read and store a lot of data also make more sense on an SSD. This ensures a significant performance boost.
However, operating systems also run excellently on HDDs, as long as enough memory is available. Large amounts of data that do not need to be accessed continuously are best stored on the HDD. This includes photos of the last vacation as well as 4K videos.
Games that do not require constant reloading
Photographs in RAW format, uncut video files
Large amounts of data that are not constantly moved
Data that needs to be accessed frequently
Operating system of the PC
How large should the hard disk memory be??
This is closely related to the respective application area of the user. When buying additional hard disk space and an SSD, everyone should be aware of how the PC will be used.
However, a combination of SSD and HDD makes sense in almost every case. Because just moving the Windows swap file to the SSD gives an enormous speed advantage when booting the system. A current Microsoft Windows 10 Professional in the 64-bit version requires 20 GB of free hard disk space alone, whereby Microsoft itself recommends keeping 32 GB free for this. The automatic installation of updates and upgrades also requires sufficient capacity on the hard drive.
Size of the cache memory
To keep the number of accesses to the HDD or SSD low, a sufficiently large buffer is important. The cache – a word originally from French that means hiding place – ensures that the access time does not have such a big impact on the overall performance of the PC.
Many HDDs today have an SSD cache. Software analyzes the read accesses to the hard disk and saves the corresponding files on the SSD when they are called for the first time (write through cache). The next time data is accessed, it is read from the SSD instead of the HDD.
In current hard disks and SSDs, up to 256 MB (mebibyte) RAM cache is now possible. Here a distinction is also made between read and write cache. However, the main memory takes over a large part of the operating system’s cache memory. Access times are shortened because communication via the hard disk bus is eliminated. A larger cache can simply hold more data. However, you hardly notice this during daily work on a desktop computer.
SSDs have a cache memory in the DRAM, which is managed by the controller’s operating system. In addition, there is also SLC cache, where in TLC and QLC systems the single cell is made available for the cache so as not to slow down the system.
The same applies here: If you need a lot of write and read processes in parallel, you should look for a larger cache memory when buying the hard disk. Casual users can easily get by with 64 or 128 MB.
Criteria when buying a hard disk
Interfaces – SATA or PCIe?
The interface standard SATA still belongs to the common format even after almost 20 years. Both HDDs and SSDs are often connected to the motherboard via SATA III. However, the SATA III standard limits the read and write speeds for SSDs. If you need faster transfers, you should use PCIe (Peripheral Component Interconnect Express) there. Among other things, it is used in SSDs in the M.2 format and, due to the small size of 22 x 42; 69 or 80 millimeters, has established itself primarily in small devices with a need for higher data rates.
When is PCIe needed?
PCIe is recommended especially for many parallel tasks. In contrast to the bus structure, serial connections are made to the switch in the chipset, so that the PCIe group connects directly to the main memory. Transfer rates of theoretically up to 16 gigabytes per second are possible here. In comparison, an SSD with a SATA III connection only delivers 600 megabytes per second – which is, however, more than sufficient for many users’ everyday tasks.
Which PCIe version?
PCIe 3.0 x4 is the most commonly available version in SSDs at the moment, as it works with the standardized host controller interface NVMe (Non-Volatile Memory Express).
PCIe 4.0 is in the starting blocks, here it will probably not be long before the standard also establishes itself in the consumer sector.
PCIe 5.0 is in the early development phase and is expected for 2020.
IOPS – important parameter for SSDs?
Another benchmark for SSDs is the IOPS value. The time of the read and write processes is measured in seconds (Input/Output per Second). Extremely fast SSDs can achieve up to 900.000 IOPS. In addition to the Total IOPS, a distinction is made between Read IOPS and Write IOPS. The access pattern and the cache settings of the hard disk’s controller are responsible for fast transfers.
However, the IOPS should not be seen as an absolute value – it is only meaningful as a relative value in a predefined test environment. Whether 60.000 or 100.000 IOPS: The differences will at most be noticeable in very large copy operations.
QLC, TLC, MLC? Which level for SSDs?
The type of NAND flash memory is named based on the availability of the memory cells. The previous standards are on up to three levels, from the single level cell to the multi-level cell and the triple level cell.
The Quadruple Level Cell, which has not been on the market that long, stores 4 bits per cell at 16 voltage levels. Thus, the capacity of the storage media is to be increased significantly.
However, practical tests show that the QLC storage has speed limitations. It is therefore recommended to give priority to the TLC standard when selecting the SSD.
Areas of application: Which solution for whom?
Depending on the industry, business solutions will be more or less lush. In the IT sector and software development, particularly many write and read operations occur. The development environment, testing and debugging require high-performance workload capacity. Slow storage solutions quickly cause frustration here.
An HDD with at least 2 TB and an SSD with at least 500 GB should nevertheless suffice for most use cases. For less demanding tasks, the storage space can be correspondingly smaller. If you only work with office applications permanently and don’t have any complex software installed, you can also get by with a 1 TB HDD and 250 GB SSD storage. The resulting write and read processes won’t stutter in this way.
Graphics-heavy tasks also require a high storage capacity. In the areas of photography and video, several GB of data quickly accumulate. Single RAW files from modern DSLRs and DSLMs are now around 80 MB. Videos in 4K amount to several GB, depending on the bit rate, even with a few minutes of runtime. HDDs with several terabytes are a must in this case. But saving in JPEG format and developing in image editing programs also take up a lot of space on the HDD. For multimedia professionals, the following therefore applies above all to the mechanical hard disk: The more, the better.
For complex games and outstanding performance, a notebook may already have 4 TB of HDD storage including an 8 GB SSD cache. In combination with a 1 TB SSD with PCIe 3.0 x4 NVMe provides enough buffer for the operating system as well as for installation files of memory-intensive games. A performance boost will always be noticeable with an SSD. This is how power, performance and speed meet. Perfect for those who need and want the best of the best. Memory-intensive games like Resident Evil 2 Remake, Anthem or Metro Exodus load much faster and run without delays. The use of fast SSDs is especially noticeable when game files have to be loaded more often.
Infrequent and occasional users
For occasional users, the purchase of an HDD with enormous capacity is not worthwhile. Those who only work a little with the PC and rarely move large amounts of data will get by excellently with common sizes like 250 GB.
Even the SSD doesn’t have to take on any oversized excesses. Pre-installed solutions or predecessor versions are usually worthwhile here. With 250 GB of NAND memory, the operating system and smaller software can be easily swapped out in order to use the memory size of the HDD for additional data.
If you want to upgrade an existing PC with more powerful components, you can safely use SSDs with SATA interface. The higher transfer rates of the PCIe standard are not needed for simple applications.