IOS differentiate cache memory physical storage logical storage

1.

The memory is divided into internal memory (memory) and external memory (external memory). ① memory Memory is the temporary storage of data in the computer, for the CPU to read directly, the data stored in it to rely on electricity to maintain, once the power loss will be lost. Therefore, when you operate the computer, you should save the information you need to save in a timely manner. Memory features: Small capacity, very fast, temporary storage of data. ② external Memory external memory includes floppy disks, hard disks, and discs, and the data stored therein is maintained by magnetism, so data can be stored permanently. External memory Features: Large capacity, slow speed, can permanently save data.

2.

Physical volume physical Volume, called PV: refers to the physical hard disk, a hard disk is a PV logical volume Group Logical Volume Group, called VG: a VG contains the whole number of PV, can be understood as a large hard disk.
Logical Volume Logical Volume, known as LV: the equivalent of a large hard disk to be logically partitioned, a VG can have a number of LV.

3.

FileSystem file System: On the basis of a logical volume, you can create a file system and then mount it to a directory so that you can use the hard drive in a file-access manner.

The visual folder is a logical store, and the system divides the area when the folder is created.
copying, pasting, and diversion. Fill, increase the expansion, all belong to the physical storage space.

4.

Cache--Memory cache--External memory

5.

According to the characteristics of the sandbox  is a logical storage, a restart of the TMP data is gone, the document and library are still there
So that means that TMP is a temporary internal memory, temporary memory, and the document and library are external memory stored on the physical hard disk. (I'm sure it's wrong to be correct.)
TMP is a first-level cache document and the library is a level two cache

6.