diff options
Diffstat (limited to 'Documentation/filesystems/ext4.txt')
| -rw-r--r-- | Documentation/filesystems/ext4.txt | 64 |
1 files changed, 23 insertions, 41 deletions
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt index 3ae9bc9..4917cf2 100644 --- a/Documentation/filesystems/ext4.txt +++ b/Documentation/filesystems/ext4.txt @@ -68,12 +68,12 @@ Note: More extensive information for getting started with ext4 can be '-o barriers=[0|1]' mount option for both ext3 and ext4 filesystems for a fair comparison. When tuning ext3 for best benchmark numbers, it is often worthwhile to try changing the data journaling mode; '-o - data=writeback,nobh' can be faster for some workloads. (Note - however that running mounted with data=writeback can potentially - leave stale data exposed in recently written files in case of an - unclean shutdown, which could be a security exposure in some - situations.) Configuring the filesystem with a large journal can - also be helpful for metadata-intensive workloads. + data=writeback' can be faster for some workloads. (Note however that + running mounted with data=writeback can potentially leave stale data + exposed in recently written files in case of an unclean shutdown, + which could be a security exposure in some situations.) Configuring + the filesystem with a large journal can also be helpful for + metadata-intensive workloads. 2. Features =========== @@ -160,7 +160,9 @@ noload if the filesystem was not unmounted cleanly, lead to any number of problems. data=journal All data are committed into the journal prior to being - written into the main file system. + written into the main file system. Enabling + this mode will disable delayed allocation and + O_DIRECT support. data=ordered (*) All data are forced directly out to the main file system prior to its metadata being committed to the @@ -201,30 +203,19 @@ inode_readahead_blks=n This tuning parameter controls the maximum table readahead algorithm will pre-read into the buffer cache. The default value is 32 blocks. -orlov (*) This enables the new Orlov block allocator. It is - enabled by default. - -oldalloc This disables the Orlov block allocator and enables - the old block allocator. Orlov should have better - performance - we'd like to get some feedback if it's - the contrary for you. - -user_xattr Enables Extended User Attributes. Additionally, you - need to have extended attribute support enabled in the - kernel configuration (CONFIG_EXT4_FS_XATTR). See the - attr(5) manual page and http://acl.bestbits.at/ to - learn more about extended attributes. - -nouser_xattr Disables Extended User Attributes. - -acl Enables POSIX Access Control Lists support. - Additionally, you need to have ACL support enabled in - the kernel configuration (CONFIG_EXT4_FS_POSIX_ACL). - See the acl(5) manual page and http://acl.bestbits.at/ - for more information. +nouser_xattr Disables Extended User Attributes. If you have extended + attribute support enabled in the kernel configuration + (CONFIG_EXT4_FS_XATTR), extended attribute support + is enabled by default on mount. See the attr(5) manual + page and http://acl.bestbits.at/ for more information + about extended attributes. noacl This option disables POSIX Access Control List - support. + support. If ACL support is enabled in the kernel + configuration (CONFIG_EXT4_FS_POSIX_ACL), ACL is + enabled by default on mount. See the acl(5) manual + page and http://acl.bestbits.at/ for more information + about acl. bsddf (*) Make 'df' act like BSD. minixdf Make 'df' act like Minix. @@ -272,14 +263,6 @@ grpjquota=<file> during journal replay. They replace the above package for more details (http://sourceforge.net/projects/linuxquota). -bh (*) ext4 associates buffer heads to data pages to -nobh (a) cache disk block mapping information - (b) link pages into transaction to provide - ordering guarantees. - "bh" option forces use of buffer heads. - "nobh" option tries to avoid associating buffer - heads (supported only for "writeback" mode). - stripe=n Number of filesystem blocks that mballoc will try to use for allocation size and alignment. For RAID5/6 systems this should be the number of data @@ -393,8 +376,7 @@ dioread_nolock locking. If the dioread_nolock option is specified write and convert the extent to initialized after IO completes. This approach allows ext4 code to avoid using inode mutex, which improves scalability on high - speed storages. However this does not work with nobh - option and the mount will fail. Nor does it work with + speed storages. However this does not work with data journaling and dioread_nolock option will be ignored with kernel warning. Note that dioread_nolock code path is only used for extent-based files. @@ -428,8 +410,8 @@ written to the journal first, and then to its final location. In the event of a crash, the journal can be replayed, bringing both data and metadata into a consistent state. This mode is the slowest except when data needs to be read from and written to disk at the same time where it -outperforms all others modes. Currently ext4 does not have delayed -allocation support if this data journalling mode is selected. +outperforms all others modes. Enabling this mode will disable delayed +allocation and O_DIRECT support. /proc entries ============= |