Here are the mount options for ext4 from the kernel documentation 3. Options ========== When mounting an ext4 filesystem, the following option are accepted: (*) == default extents (*) ext4 will use extents to address file data. The file system will no longer be mountable by ext3. noextents ext4 will not use extents for newly created files journal_checksum Enable checksumming of the journal transactions. This will allow the recovery code in e2fsck and the kernel to detect corruption in the kernel. It is a compatible change and will be ignored by older kernels. journal_async_commit Commit block can be written to disk without waiting for descriptor blocks. If enabled older kernels cannot mount the device. This will enable 'journal_checksum' internally. journal=update Update the ext4 file system's journal to the current format. journal=inum When a journal already exists, this option is ignored. Otherwise, it specifies the number of the inode which will represent the ext4 file system's journal file. journal_dev=devnum When the external journal device's major/minor numbers have changed, this option allows the user to specify the new journal location. The journal device is identified through its new major/minor numbers encoded in devnum. noload Don't load the journal on mounting. data=journal All data are committed into the journal prior to being written into the main file system. data=ordered (*) All data are forced directly out to the main file system prior to its metadata being committed to the journal. data=writeback Data ordering is not preserved, data may be written into the main file system after its metadata has been committed to the journal. commit=nrsec (*) Ext4 can be told to sync all its data and metadata every 'nrsec' seconds. The default value is 5 seconds. This means that if you lose your power, you will lose as much as the latest 5 seconds of work (your filesystem will not be damaged though, thanks to the journaling). This default value (or any low value) will hurt performance, but it's good for data-safety. Setting it to 0 will have the same effect as leaving it at the default (5 seconds). Setting it to very large values will improve performance. barrier=<0|1(*)> This enables/disables the use of write barriers in the jbd code. barrier=0 disables, barrier=1 enables. This also requires an IO stack which can support barriers, and if jbd gets an error on a barrier write, it will disable again with a warning. Write barriers enforce proper on-disk ordering of journal commits, making volatile disk write caches safe to use, at some performance penalty. If 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. 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./ 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./ for more information. noacl This option disables POSIX Access Control List support. reservation noreservation bsddf (*) Make 'df' act like BSD. minixdf Make 'df' act like Minix. 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 nogrpid (*) New objects have the group ID of their creator. sysvgroups resgid=n The group ID which may use the reserved blocks. resuid=n The user ID which may use the reserved blocks. sb=n Use alternate superblock at this location. quota noquota grpquota usrquota 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 disks * RAID chunk size in file system blocks. delalloc (*) Deferring block allocation until write-out time. nodelalloc Disable delayed allocation. Blocks are allocation when data is copied from user to page cache. |
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