Which of the following Linux filesystems preallocates a fixed number of inodes at the filesystem's make/creation time and does NOT generate them as needed?
(Choose TWO correct answers.)
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A. B. C. D. E.AC
The correct answers are C. ext2 and D. XFS.
A filesystem inode is a data structure used to store information about a file or directory in Linux. It contains metadata such as the owner, permissions, creation/modification/access times, and pointers to the data blocks where the file's content is stored. Each inode is identified by a unique number (inode number or i-number) within the filesystem.
When a new file or directory is created in Linux, a new inode is allocated and initialized with the necessary metadata. Therefore, the number of inodes required for a filesystem depends on the number of files and directories it contains. If a filesystem runs out of inodes, it cannot create new files, even if there is free space available.
However, some Linux filesystems preallocate a fixed number of inodes at the filesystem's creation time, instead of generating them as needed. This approach can help to prevent fragmentation and improve performance, especially if the filesystem is expected to contain a large number of small files or directories.
Here are the explanations of the two filesystems that preallocate inodes:
C. ext2 (Second Extended Filesystem) is an old Linux filesystem that was widely used before the advent of ext3 and ext4. It preallocates a fixed number of inodes at filesystem creation time, based on the size of the filesystem and the expected number of files/directories. The default inode ratio is 1 inode per 16 KB of filesystem space. Therefore, a 1 GB ext2 filesystem would have approximately 64,000 inodes preallocated. Once the inodes are exhausted, no new files or directories can be created, even if there is free space available. To avoid this, the administrator can tune the inode ratio at filesystem creation time using the -i option of the mkfs.ext2 command.
D. XFS is a high-performance journaling filesystem that is commonly used in enterprise environments. It also preallocates a fixed number of inodes at filesystem creation time, based on the expected number of files/directories and the inode size. The default inode ratio is 1 inode per 2 MB of filesystem space. Therefore, a 1 TB XFS filesystem would have approximately 500,000 inodes preallocated. Like ext2, XFS also allows the administrator to tune the inode ratio at filesystem creation time using the -i option of the mkfs.xfs command.
A. ext3 (Third Extended Filesystem) is a journaled version of ext2 that added improved reliability and performance. Unlike ext2, it generates inodes as needed and does not preallocate them at filesystem creation time. Therefore, it can dynamically adjust the number of inodes based on the filesystem usage.
B. JFS (Journaled File System) is another high-performance journaling filesystem that was developed by IBM. Like ext3, it generates inodes as needed and does not preallocate them at filesystem creation time.
E. procfs is not a filesystem that stores files on a disk. Instead, it is a virtual filesystem that provides a view of the running processes and kernel information. Therefore, it does not have inodes or allocate disk space for files.