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Diffstat (limited to 'Documentation/filesystems/ext4.txt')
| -rw-r--r-- | Documentation/filesystems/ext4.txt | 51 |
1 files changed, 30 insertions, 21 deletions
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt index 0d5394920a3..174eaff7ded 100644 --- a/Documentation/filesystems/ext4.txt +++ b/Documentation/filesystems/ext4.txt @@ -2,19 +2,24 @@ Ext4 Filesystem =============== -This is a development version of the ext4 filesystem, an advanced level -of the ext3 filesystem which incorporates scalability and reliability -enhancements for supporting large filesystems (64 bit) in keeping with -increasing disk capacities and state-of-the-art feature requirements. +Ext4 is an an advanced level of the ext3 filesystem which incorporates +scalability and reliability enhancements for supporting large filesystems +(64 bit) in keeping with increasing disk capacities and state-of-the-art +feature requirements. -Mailing list: linux-ext4@vger.kernel.org +Mailing list: linux-ext4@vger.kernel.org +Web site: http://ext4.wiki.kernel.org 1. Quick usage instructions: =========================== +Note: More extensive information for getting started with ext4 can be + found at the ext4 wiki site at the URL: + http://ext4.wiki.kernel.org/index.php/Ext4_Howto + - Compile and install the latest version of e2fsprogs (as of this - writing version 1.41) from: + writing version 1.41.3) from: http://sourceforge.net/project/showfiles.php?group_id=2406 @@ -32,28 +37,26 @@ Mailing list: linux-ext4@vger.kernel.org you will need to merge your changes with the version from e2fsprogs 1.41.x. - - Create a new filesystem using the ext4dev filesystem type: + - Create a new filesystem using the ext4 filesystem type: - # mke2fs -t ext4dev /dev/hda1 + # mke2fs -t ext4 /dev/hda1 - Or configure an existing ext3 filesystem to support extents and set - the test_fs flag to indicate that it's ok for an in-development - filesystem to touch this filesystem: + Or to configure an existing ext3 filesystem to support extents: - # tune2fs -O extents -E test_fs /dev/hda1 + # tune2fs -O extents /dev/hda1 If the filesystem was created with 128 byte inodes, it can be converted to use 256 byte for greater efficiency via: # tune2fs -I 256 /dev/hda1 - (Note: we currently do not have tools to convert an ext4dev + (Note: we currently do not have tools to convert an ext4 filesystem back to ext3; so please do not do try this on production filesystems.) - Mounting: - # mount -t ext4dev /dev/hda1 /wherever + # mount -t ext4 /dev/hda1 /wherever - When comparing performance with other filesystems, remember that ext3/4 by default offers higher data integrity guarantees than most. @@ -104,8 +107,8 @@ exist yet so I'm not sure they're in the near-term roadmap. The big performance win will come with mballoc, delalloc and flex_bg grouping of bitmaps and inode tables. Some test results available here: - - http://www.bullopensource.org/ext4/20080530/ffsb-write-2.6.26-rc2.html - - http://www.bullopensource.org/ext4/20080530/ffsb-readwrite-2.6.26-rc2.html + - http://www.bullopensource.org/ext4/20080818-ffsb/ffsb-write-2.6.27-rc1.html + - http://www.bullopensource.org/ext4/20080818-ffsb/ffsb-readwrite-2.6.27-rc1.html 3. Options ========== @@ -177,6 +180,11 @@ barrier=<0|1(*)> This enables/disables the use of write barriers in your disks are battery-backed in one way or another, disabling barriers may safely improve performance. +inode_readahead=n This tuning parameter controls the maximum + number of inode table blocks that ext4's inode + 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. @@ -209,15 +217,17 @@ noreservation bsddf (*) Make 'df' act like BSD. minixdf Make 'df' act like Minix. -check=none Don't do extra checking of bitmaps on mount. -nocheck - debug Extra debugging information is sent to syslog. errors=remount-ro(*) Remount the filesystem read-only on an error. errors=continue Keep going on a filesystem error. errors=panic Panic and halt the machine if an error occurs. +data_err=ignore(*) Just print an error message if an error occurs + in a file data buffer in ordered mode. +data_err=abort Abort the journal if an error occurs in a file + data buffer in ordered mode. + grpid Give objects the same group ID as their creator. bsdgroups @@ -243,8 +253,6 @@ nobh (a) cache disk block mapping information "nobh" option tries to avoid associating buffer heads (supported only for "writeback" mode). -mballoc (*) Use the multiple block allocator for block allocation -nomballoc disabled multiple block allocator for block allocation. 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 @@ -252,6 +260,7 @@ stripe=n Number of filesystem blocks that mballoc will try delalloc (*) Deferring block allocation until write-out time. nodelalloc Disable delayed allocation. Blocks are allocation when data is copied from user to page cache. + Data Mode ========= There are 3 different data modes: |