Although you can't afford to buy a house, it is still affordable to let the little sisters live in a large space (hard disk). Large-capacity solutions are of course mechanical hard disks, but the same is HDD, but there are CMR and SMR and other different technologies, if you feel that "enterprise-class hard disks", "NAS special disks" can be assured to buy, then you can be a sample. As long as you don't want all the little sisters in the hard disk to disappear, please follow the author on the road from getting started to giving up.
One cry, two troubles, three on Yuya
In the long history of computers, mechanical hard disks are not historical, but technology has undergone many changes.
The capacity of a single disk determines the total capacity of the hard disk (image from Tencent)
The early hard disk uses LPR, that is, horizontal magnetic recording, because the density of magnetic materials is small, and the single disk capacity is only 160G, resulting in a very limited hard disk capacity, and hard disk manufacturers are constantly innovating technology to break through the bottleneck.
Vertical magnetic recording density is higher
Later, PMR, that is, vertical magnetic recording technology, greatly increased the density of magnetic materials, and the capacity of a single disc can reach 1.5T, which naturally eliminated the LPR hard disk.
PMR hard drives have become mainstream
With the development of technology, PMR hard disks are further subdivided into CMR (traditional magnetic recording) and SMR (stacked tile magnetic recording), the difference between the two is the difference in capacity density, and the technology behind it is the different track spacing.
CMR traditional magnetic recording leaves a certain gap between the tracks to avoid data interference between different tracks, whether writing or reading, the head is passed above the track to complete the read and write operations.
Comparison of traditional magnetic recording (top) and tile-mounted magnetic recording (bottom).
However, the safe distance between the tracks allows the capacity of the disk to have an upper limit, so the manufacturer will close the distance of the tracks to accommodate more tracks on the platter, which is the SMR tile magnetic record.
Overwriting the SMR results in duplicate writes
But the problem also comes, because the writing head is larger than the brush area of the reading head, which will cause the data of the next track to be erased when writing data, and it is necessary to back up the data of the next track first, but when writing the next track data, it will erase the data of the next track, and the solution is to set a safe distance at every part of the track, and use a large-capacity buffer area to place the data.
SMR is criticized by users because when the hard disk stores more data, even if it is a small data change, it will repeatedly migrate the data in the sector, which will not only affect the write speed, but also accelerate the aging of the platter and head, and the risk of data storage will increase.
Of course, SMR is not useless, in laptops or space-critical environments, higher data density can provide greater capacity, and the price will be slightly lower than CMR.
Select the hard disk according to the actual needs
So how should users choose? If it is a large file and will not be written and modified frequently (such as simply storing high-definition movies), the experience of CMR and SMR two hard disks will not be significantly different; in addition, for the vast majority of users, the author recommends preferring cmR hard disk, whether playing games or playing sisters are more at ease.
So the question is, in the product page of mechanical hard disk, manufacturers are secretive about what kind of storage technology is used in the hard disk, or simply write a PMR technology, how do we judge which kind of hard disk it is?
You can tell which hard drive it belongs to by model number
The most reliable is to see the specific model of the product: the vast majority of commercially available mechanical hard disk models only correspond to one technology, as long as you search the model on the Internet, you can find out whether it is CMR or SMR. The auxiliary method is to look at the parameters of the hard disk, the general 3.5-inch CMR hard disk single disk capacity is about 1T, and the 2.5-inch CMR hard disk single disk capacity is about 600G, much higher is basically SMR; generally more than 5900 rpm high speed is CMR, on the contrary, low speed is SMR, but can not be generalized; most of the cache is less than or equal to 64M is CMR hard disk, greater than or equal to 128M is SMR hard disk.
The following hard disks are CMR hard disks, when purchasing, we must see the model, CMR and SMR often have only one letter difference in the model, so the similarity of the model can not be used as a judgment standard.
Combining the above points, we can judge which technology is used in the mechanical hard disk, remember to use the environment-oriented, often read and write data do not put in the SMR hard disk, and then you can happily place a single!
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