Storage devices is the first topic that anyone studying and working in the storage industry should be related to; it is the foundation for a good understanding of how the storage systems are integrated into the whole IT infrastructure. If you are starting your professional career as a system or storage administrator or are just planning to fit in the IT staff, this topic should concern you; feel free to use it as a reference. The storage devices might include several categories and types, but is not my intention to mention all of them, simply because they might be already obsolete technologies (like floppy diskettes), are not associated with this industry or are just out of the scope of what I want to introduce here.
Storage devices might also be referred to as storage media or just “storage”; and are defined as any hardware device capable of storing and processing information/data permanently or temporarily. There are two main categories used by storage systems, non-persistent (volatile) and persistent (non-volatile) storage; in general computing systems, these categories are better known as primary and secondary storage, respectively. Notice that the use of the word “hardware” in the definition might be ambiguous, due to the recent introduction of cloud storage solutions.
Even when could be a variation of this categorization, you will found that is mostly to be like so. For keeping it simple, from now on I will use only persistent and non-persistent when referring to the categories shown in the left image.
The non-persistent devices are the ones that won't preserve the information stored on them, so when the system they are attached to is shut down or lose the contact with the power, the information will be wiped out. The best example for this type of storage is RAM-based devices that are primary use to boost the performance of the computing systems by caching the data. The CPU also fits into this category and it is put in front of the RAM for caching operations, due to the fastest data access speed, but smaller size.
The persistent storage devices, on the other hand, allows you to keep your data stored even when the devices are not connected to the power. Devices such as HDD, SSD, Tapes, Compact Discs (CD, DVD, and Blu-ray) and flash memories, are the common types found in this category. HDDs and SDDs are the main devices used in storage arrays for storage networking, where tapes, are commonly used as storage backup.
Non-persistent and persistent storage devices also can be grouped as their used technology. The main technologies used are semiconductor, magnetic, and optical. Every type of device can be also classified by different technologies such as form factor, connection type, access speed and others.
Now, that we have a basic understanding of the storage device category, technologies, and types, we can summarize them with the image below.
For data center or enterprise storage solutions, CPUs, RAM, SSDs, HDDs and Tapes are the devices that are going to rule the storage industry; and those are the one I am going to give more attention and I’ll be writing about soon, they include other individual and interesting must-mention topics.