Many friends who have just started SSD may have doubts about the SSD capacity identification. Take the Samsung 860 PRO 1TB SSD as an example. It stands to reason that 1TB=1024GB, but only 953GB can be seen on the computer. Some SSDs It will even be lower or even lower than this value. What is the situation? Is it difficult to cut corners? Actually, the reason is not the case.
To understand this problem, we must start with the working mechanism of solid-state drives.
1TB capacity free space 953GB
It is believed that friends who buy SSDs will hear the concept of 'balanced reading and writing' and GC 'garbage collection' more or less. These two functions are based on a module called OP reserved space.
As we all know, when the SSD writes new data, it must erase the original data. Therefore, in order to avoid overwriting invalid pages in the SSD, The SSD controller's garbage collection function uses OP reservations as temporary workspaces to manage planned invalid page merges and to reclaim blocks that fill up with invalid (or deleted) pages.
These recycled pages and blocks are added to the reserved space, which helps the SSD master to write and ensure that it maximizes the hard disk performance during the highest load.
Because SSD read, erase, modify all invalid pages and write it back to the block that has partially filled in invalid pages will have a large impact on performance, SSDs will become very slow. Garbage collection is independent of the operating system The operation will be triggered automatically when the activity is infrequent, periodically or when the corresponding ATA data set management TRIM command is issued, to arrange garbage collection.
With this space reserved, SSDs can always provide free blanks that are always available through over-provisioned storage capacity to help maintain effective wear-leveling on NAND flash because SSD controllers can be intelligent on all NAND flash chips. Evenly distribute write operations without affecting the overall performance of the SSD during the highest traffic load.
In addition, the ATA dataset management TRIM command can increase the free space of the SSD by reclaiming any invalid pages and unused user capacity.
therefore, It is very important for solid-state hard disks to reserve space for OPs. Everyone shouldn't go to the small percentage of space.
OP reserved space is divided into several parts?
The OP reserved space is divided into three layers. The OP capacity of the first layer is generated due to the unit conversion problem. The nominal capacity is in kilobytes, that is, 1GB=1000MB, and the NAND flash memory particles are 1024, ie, 1GB. 1024MB, where the difference in the space value is the capacity of the first layer, this capacity can not be changed, but also a fixed and constant access to all brands, this difference is about 7.37% of the nominal capacity of the SSD.
The second-level OP capacity depends on the SSD design company and the main control company's positioning of the product. For example, if a 256GB SSD has 240GB/250GB/256GB or even 200GB, the difference in capacity lies in the difference between the manufacturers. Layer 2 OP capacity settings.
It cannot be said absolutely that the more the second-level OP capacity is, the better the product performance is. It can only be said that all other conditions are set aside, and the more reserved second-level OP space, the more able to improve the solid-state main control mechanism such as GC recovery, wear and balance performance. , In order to enhance and maintain the long-term high-speed solid-state drive without losing speed.
OP space layered map
The third-layer OP capacity is the space that users can choose to set by themselves. Its function is also consistent with the second-level OP space.
However, because the setting of OP space will reduce the space capacity that SSDs can actually use, especially in the early days of SSD development, SSDs are relatively expensive, so many consumer-grade SSDs cancel the third-tier OP space setting, but now Most SSDs have a third-tier OP space, and even some brands already support setting up OP space.
Set up the third layer of OP reserved space tutorial
Here we take the Samsung 860PRO as an example to demonstrate the setup of the OP reserved space. It is very simple. There is almost no threshold.
Samsung 860PRO
To set the reserved space for the Samsung SSD, first you need to download Magician software, which is Samsung's official SSD management software.
Magician
In this software, we can check the SSD related information, write volume, firmware version. Here we click on the 'Over Provisioning' below.
Then click 'Run Over Provisioning' to enter the OP reservation space setting interface.
Set up OP space
have to be aware of is, The OP space setting is at least 1% of the hard disk capacity, and the maximum is 50%. For light users, 1% is sufficient, and even heavy users should not exceed 10%. After all, each gigabyte of capacity is bought by Hua Yinzi. After setting up a large-capacity OP space, it cannot be used. It is very wasteful.
Well, the contents of the reserved space for the SSD OP are here. Have you learned it?
