What is disk formatting?
In simple terms, disk formatting is a kind of preparation of a data storage device (for example, an external or internal HDD or SSD or a USB flash drive) for use. Usually it is a three-stage process that consists of low-level formatting, partitioning and high-level formatting.
Low-level is a physical type of formatting that is typically performed by the manufacturer. It consists in dividing a blank disk into cylinders, tracks and sectors of 512 or 4096 bytes, or 520 bytes in case of SAS disks. When it’s performed on a drive with data, all its files are irreversibly erased. Low-level formatting is not something that an ordinary user should do and even more, it shouldn’t be done on a regular basis, as it may damage the drive and shorten its service life.
Partitioning, in its turn, can be operated by a user. Basically, it is a division of a disk into one or more logical parts, so-called partitions. It’s performed for convenience purposes and in order to increase disk performance.
And the last, but not the least, high-level or logical formatting. It’s just the thing the majority of the users refer to when they say “formatting”. It’s a process of generating boot information, writing a file system, dividing a disk into clusters, and so on. A cluster is a logical data storage unit in the file allocation table that unites a group of sectors. For example, on a disk with sectors of 512 bytes, a 512-byte cluster contains 1 sector, and a 4KB-cluster contains 8 sectors.
The logical type of formatting is mainly done by a user in order to:
- put into use a new drive;
- reinstall the operating system;
- change the file system or drive size;
- get rid of multiple viruses;
- get access to an inaccessible drive.
In general, it can be performed in two ways: quick and full (or general).
Full and quick format. What is the difference?
As its name indicates, a quick format is faster than a full one. When you choose the Quick format option, the data is "deleted", the partition table is rebuilt and the file system is replaced. However, this type of format doesn’t imply real elimination of data. In fact, it only deletes the journal with the information about the files and their locations on the drive. So, after a quick format, the data becomes inaccessible for a user, but remains on the drive and can be recovered with the help of a special data restore program.
When you run a full format, the files are completely eliminated and the drive itself is additionally scanned for bad sectors. If there are any logical bad sectors, they will be fixed in the process. Actually, this scan is one of the factors that make the full format twice as long as the quick one. Apart from that, when a drive is fully formatted, its partition table is overwritten, no matter if it’s MBR (Master Boot Record), GPT (GUID Partition Scheme) or APM (Apple Partition Map), and the previous file system is replaced with a new one. So, after a full format, all the data is cleared from the storage and could not be restored with data recovery software.
Let’s summarize. In case you need to format a brand-new data storage device, you should perform a full format. But if your drive has been already formatted and you are absolutely sure that it doesn’t have damaged nor logical bad sectors, a quick format would be enough. Nevertheless, note that bad sectors can damage your drive and if some information is saved to such a sector, it may be read with errors or even get corrupted. So, when you doubt if there are any logical bad sectors on your disk, you’d better choose the full variant.
And before selling or donating your drive, we strongly recommend you thoroughly clear all sensitive information by performing a full format.
