Method of enabling ext4 file system in Fedora 9


Provide ext4filesystemSupport for is the biggest highlight of Fedora 9, but ext4 is only optionalinstall, direct accessinstallProgram, there is no ext4 option. If you want to enable ext4, you need to start it after the CD is startedinstallPress the tab key on the startup options andcommandAdd the kernel option ext4 to the line in order toinstallWhen using ext4. It should be noted that ext4 is still in the dev stage, and grub does not support ext4 as the boot partition, so if the / partition uses ext4, the / boot partition needs to be independent and placed on the non ext4 partition, otherwisesystemWill not start.

After the disc is started, ininstallPress the tab key on the startup option, and then add the kernel option ext4 on the command line. When partitioning, the option ext4dev will appear.

ABOUT ext4:

Because the inode of ext3 uses 32 address pointers and 3 indirect pointers, the maximum size of a single file is 2 ^ 10 * 2 ^ 10 * 2 ^ 10 * 2 ^ 11, that is, the 41st power of 2, that is, when 4K blocks are used on 32 systems, the maximum size of a single file is 8tb. Due to the 32-bit address length, ext3 supports a maximum disk size of 2 ^ 31 * 4K, that is, 8tb (inode number is a signed int variable, so it is 2 ^ 31).
Due to the development of today’s disk arrays, there have been more than 8tb disk arrays, so there has been a heated discussion on ext3 expansion in the kernel mailing list recently, which is ext4.
After a look, those ext3 / ext2 developers used the following inode to replace the original ext3_ Inode structure

struct ext3_extent { __le32 ee_block; /* first logical block extent covers */ __le16 ee_len;  /* number of blocks covered by extent */ __le16 ee_start_hi; /* high 16 bits of physical block */ __le32 ee_start; /* low 32 bits of physical block */    };

The last 15 indirect indexes are used for storing files; Ext4 now replaces ext3 with an inode called an extension_ Inode, or ext3_ extent。
The space of ext takes up 3 bytes, so that the original 15 pointer spaces can store 5 ext. if the file is continuous enough, it can store 5 × 2 ^ 16byte (320kbyte) file. When the original ext3 does not use indirect index, it can only store files with the size of 48 kByte, which reduces the number of small files (not big or small files?) Pointer index times, which speeds up the access time.
When a file exceeds a certain size, ext also uses an indirect index. However, unlike ext3, there is no limit to the number of indirect indexes of ext, unlike ext3, which can only do three indirect indexes at most.
Attention EE_ Len field, which is 16 bits, that is, its maximum block group is 64K, not 4K. This greatly reduces the search time. Ext4 developers explained that “now file storage tends to use continuous blocks, which will not waste space”.
Another important field is: EE_ Start and EE_ start_ Hi, they form a 48 bit disk block index,
This can support 1024 Pb devices, which will be enough in the coming decades!
But ext4 has a disadvantage, that is, the old kernel can not recognize the disks using ext4.