You can see an error code indicating that the storage file system is unix. There are several ways to solve this problem, and we will talk about them a little later.
tmpfs is a temporary file storage paradigm implemented in many Unix-like operating systems. It should look like a mounted filesystem, but the data is stored in volatile memory, not read-only memory.
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What Is A Memory-based File System (RAM Disk)?
A storage-based file system creates a storage area directly in the computer’s RAM, as if it were a partition on a hard disk. Since RAM is a type of volatile storage, this means that in the event of a system restart or failure, the file system will be lost along with all data.
The main advantage of storage-based file systems is their very high speed – ten times faster than today’s solid state drives. Reading performance and reading The writing has been greatly improved for all types of workloads. These types of fast storage areas are ideal for applications that constantly require small areas of data for staging or temporary storage. Since the data will be lost when the computer is rebooted, it cannot be valuable, because even the backup schedule cannot guarantee that all data will be replicated in the event of a system failure.
12.4 Allocation Methods
- There are three main methods of storing files on disk: contiguous, linked, and indexed.
12.4.1 Linked mission
- Continuous placement requires all blocks in a file to be together continuously.
- Performance is very high because reading sequential blocks of the same file usually does not require moving the disk heads or at most a small step to the next adjacent cylinder.
- Memory allocation has the same issues discussed earlier for allocation Contiguous blocks of memory (first match, best match, fragmentation problems, etc.). The difference is that the hefty waste of time moving the plates from point to point can now justify the benefits of keeping the files continuous when possible.
- (Even filesystems that do not store files contiguously by default can benefit from some utilities that compress the hard drive, making all files contiguous.)
- Problems can arise when files get larger or when the exact file size is not known at the time of creation:
- Overestimating the final file size increases external fragmentation and wastes disk space.
- Due to underestimation, it may be necessary to move the file or end the process if the file size exceeds the originally allocated space.
- If a file grows slowly over a long period of time and all of the last space must be allocated first, a lot of space becomes unusable before the file fills up the space.
Figure 12.5 – Continuous allocation of disk space
12.4.2 Associated assignment
- Files on disk can be saved as linked lists using the space for each link. (For example, the block size might be 508 bytes instead of 512.)
- A bound distribution does not require external fragmentation, does not require known file sizes, and allows files to grow dynamically at any time.
- Unfortunately, the linked assignment is only effective for sequential access files, since random access must start at the top of the list for each new location access.
- Spreading block clusters reduces the space consumed by pointers through internal fragmentation.
- Another major issue with bound mapping is its reliability in the event of a missing or damaged pointer. Doubly linked lists offer some protection at the cost of additional overhead and wasted storage space.
Figure 12.6 – Associated distribution of space
- The file allocation table (FAT) used by DOS is a variant of linked allocation in which all links are stored in a separate table at the beginning of the hard drive. The advantage of this approach is that the FAT table can be cached in memory, which greatly increases the speed of random access.
Figure 12.7 File Allocation Table
12.4.3 Indexed assignment
- Indexed mapping combines all the indexes to access each file in a common block (for that file) instead of spreading them across the hard disk or storing them in a FAT table.
Figure 12.8 – Indexed space allocation
- Some storage space is wasted (compared to linked lists or FAT tables) because each file must be assigned an entire index block, no matter how many data blocks the file contains. This leads to questions about the size of the inode and how it should be implemented. There are different approaches:
- A related schema – an index block is a disk block that can be read and written in one disk operation. The first index block contains header information, addresses of the first N blocks, and optionally a pointer to additional associated index blocks.
- Multi-level index – The first block of an index contains a series of pointers to the blocks of the secondary index, which in turn contain pointers to the actual blocks of data.
- A combination schema is a schema used in UNIX inodes where the first 12 data block pointers are stored directly in inodes, followed by single, double and Triple indirect pointers provide access to additional blocks of data. if it’s necessary. (See below.) The advantage of this scheme is that for small files (of which there are many) blocks of data are readily available (up to 48 KB for 4 KB blocks). Files up to 4144 KB (with 4 KB blocks) can be accessed with only one indirect block (which can be cached), and large files can still be accessed with relatively few hits. (in theory, it is possible to address addresses greater than 32-bit, so some systems have switched to 64-bit file pointers.)
Figure 12.9 – UNIX inode.
- The optimal distribution method is different for sequential files from random access files, and for small files and large files.
- Some systems support more than one distribution method, which may require specifying how the file will be used during distribution (sequential or random access).Such systems also provide conversion utilities.
- Some systems are known to use continuous access for small files and automatically switch to an indexed schema when the file size exceeds a certain threshold.
- And, of course, some systems adjust their display schemes (for example, block sizes) to best match the hardware properties for optimal performance.