Question

SMR (shingled magnetic recording): more storage density

Answer 1

On the trail of shingled magnetic recording (SMR)
SMR hard drives: features
SMR compared to other storage technologies
In which cases is SMR used?

---

SMR (shingled magnetic recording): more storage density

The world is hosting more and more data: mobile devices, streaming , clouds, servers ... Data consumption per household is expected to soon reach one terabyte per month . How can you meet this growing demand for storage capacity? The answer could be SMR ( shingled magnetic recording ). We tell you what staggered magnetic recording is, how this new technology works and how much storage capacity it provides..

Index

1. On the trail of shingled magnetic recording (SMR)
2. SMR hard drives: features
3. SMR compared to other storage technologies
4. In which cases is SMR used?

On the trail of shingled magnetic recording (SMR)

For a long time, hard drives seemed to have reached their capacity limit at four terabytes, as there had been no great progress since then. And then there was Shingled Magnetic Recording (SMR ), which makes it affordable to generate eight-terabyte hard drives. What's most surprising about SMR hard drives is their areal density, offering more than 25 percent additional storage space on the same physical surface .

Note

To understand SMR, you need to know the structure of a hard drive , which is made up of cylinders, platters, tracks, and sectors. The latter are small sections where the data is written. From a physical point of view, platters are discs with a front and a back, each with a read and write head. Its surface, in turn, is divided into circular tracks that are stacked on the disk and, together, form the cylinder..

So what is SMR? In simple terms, shingled magnetic recording is a hard drive technology in which the distance between tracks is further reduced. The English term shingle means? Tile? and it graphically describes how the process works, because the tracks on the SMR hard drive overlap like tiles on a roof , allowing more data to be written to the same space. With the SMR, the read heads are much smaller than the write drives, which means that they can read all the data, even if the tracks are overlapping.

This technology is still new but very promising, and could soon replace the current standard, perpendicular magnetic recording or PMR ( perpendicular magnetic recording ), which uses a parallel track design in which the poles of the magnetic elements (representing bits of data) are oriented perpendicular to the surface of the disc and the magnetic tracks are written side by side without overlapping. To get more capacity with PMR, you have to expand the surface area, underlining the enormous potential of shingled magnetic recording . The SMR is an extension of the PMR and offers an improved areal density , so the final product has the same physical appearance as a standard PMR hard disk but a much higher capacity. However, the change in architecture of the SMR hard drive also means that the user experience is very different..

SMR hard drives: features

SMR hard drives shift their focus to overcome the physical limitations of a normal hard drive, starting with the relatively wide read / write head, even considerably wider than the tracks themselves. The head writes the data tracks sequentially. Part of the tracks are overwritten, and since they overlap, adjacent tracks must be overwritten each time. In theory, this would mean that changing a single byte would force the entire SMR hard drive to be overwritten and data processing would become so slow that staggered magnetic recording would be completely useless.

To prevent this from happening, the SMR combines the tracks into so-called bands . This limits the overlapping of the tracks, and therefore their overwriting, to a certain number. Additionally, each hard drive has an internal buffer zone for temporary storage and a cache. The data is first written to these two intermediate locations and only then is it entered in the correct place on the track. This explains why SMR drives often continue to function for a long time after a write operation.

The system uses a very powerful writing element to create very narrow tracks, which leads to a higher data density. This makes the SMR ideal for continuous writing of data to the hard disk in long sequential writing processes.

SMR compared to other storage technologies

A major drawback of the SMR is that it is still a very young technology and that it is not always clearly specified on all hard drives. In fact, it is often the case that hard drives marked as suitable for the NAS are actually staggered magnetic recording models. In principle, an SMR hard drive can also be used in the NAS, but due to its design, changing workload requirements mean that the limit is quickly reached.

If you use several types of hard disk, for example, to augment a server with SSD, you should avoid combining PMR and SMR , as some models have proven to give performance problems in these cases.

In theory, an SMR can be used like any other hard disk, that is, it can be formatted in FAT32 and run on Windows. In direct comparison to a conventional PMR hard drive, the data transmission speed varies greatly for the reasons mentioned above, at least when the write access becomes erratic. With an SMR hard drive, if processes are linear, speed is not affected. Likewise, there are no notable differences in reading. In any case, while it is true that shingled magnetic recording works better than what is usually believed compared to other storage technologies, it is not capable of ending the dominance of SSD hard drives as drives for games or programs, but also it is true that it was not designed for this.

In which cases is SMR used?

SMR takes full advantage of when the system must continually write data to the hard drive. These lengthy sequential write processes are required for server applications, backups, and archive data : for example, for files in the cloud or for object-based storage architectures.

These discs are not recommended for private use (for example, as a large hard drive for a personal computer) due to the heat and noise they generate and their high power consumption . The cause of these inconveniences is the reorganization method mentioned above; new data is initially written to an empty area of ​​the disk, while old data is temporarily held on the original track. When the SMR hard drive is idle, the old data bits are replaced with the new ones. To do this, SMR requires intermediate downtime. The hard drive can become noticeably slower if it has to write data to randomly distributed addresses over a long period of time, which is called a random write.

Manufacturers of SMR hard drives aim to solve this problem through firmware . However, SSD hard drives are still the best option for regular and private use , especially since they are getting cheaper and cheaper.

If you instead want to create a data file on your server, the SMR offers you a solution that saves physical space, is cost-effective and reliable.

---