nvme ssd What the! NVMe does not support TRIM? You can’t go wrong with it…
ddr 4 8gbSSD OEM nvme ssd is nvme ssd, you read that right nvme ssd， NVMe’s SSDs do not support TRIM!
what’s going on here?
a little bit about the development of SSDs.
SSDs were developed during the SATA era. The original SSD speed was slow and the unit price was high, and the sequential read and write speed was not as fast as the hard disk. However, the iterative development of semiconductors is very fast, and soon catches up with and surpasses ordinary hard disks.
but at that time, the SSD still used the SATA interface, because the storage at that time was the world of SATA HDD, if your SSD is not compatible with SATA, who is it sold to? <
p data-pid = “yqHA11jM”> SSDs are inherently different from HDDs. What are the essential differences?
here, the first is the advantage of the SSD, and the second is the characteristics of the SSD. The third is the fatal flaw of SSDs.
so, the SSD is at the time of writing. The strategy adopted is to read out the blocks that need to be overwritten, make data modifications, and then write them to a new, erased place. Eventually, garbage blocks are periodically recycled and erased inside the SSD.
the space of the SSD at the beginning is very empty, there are many useless blocks, write casually. As usage increases, if no blocks are available at write time, you can only wait for the block to finish erasing before writing. At this time, you will find that the SSD performance is very poor.
Next, let’s talk about how the operating system manages deleted files. This is very simple, the file system will make a mark on the file header, indicating that the file is deleted. This operation may be said to be instantaneous. Then this management method, coupled with the write operation of the SSD, leads to poor SSD performance. Why?
imagine that we fill an SSD with files and then delete those files. For the file system, the entire disk is empty. But for SSDs, the entire disk is data. Because the deleted data is only marked with deletion bits, the SSD does not know that this space can be used reasonably, thus erasing and writing in advance.
smart you see here, come up with a solution! That is, when the operating system deletes files, tell the SSD that these places have been deleted, and the SSD you can handle at will, erasing in advance! In this way, the SSD can arrange the space reasonably.
which is where TRIM comes from. Operating systems that support TRIM, when deleting files, will tell the SSD master that those places are deleted data.
it looks like TRIM is very good. However, there is also one place to pay attention to, which is related to data recovery. Just mentioned that the operating system just makes a mark of deleted files and does not really delete them, so once you delete them by mistake, you can get back the accidentally deleted files through some recovery tools. But once the operating system gives the SSD a TRIM instruction and the SSD is recycled, then even if you use the tool to recover, the recovery is a pile of junk data.
in addition, TRIM simply tells the SSD that these places can be recycled, rather than forcing the SSD to recycle. Therefore, the SSD master can choose not to recycle, or delay recycling.
well, back to the question of the title. NVMe SSDs do not support TRIM because TRIM is a SATA instruction! NVMe uses a completely new protocol. The equivalent of the SATA TRIM directive in NVMe is Deallocate. In addition, for SCSI, the corresponding is not TRIM, but UNMAP.
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