Reiserfs Mount Options Continued: Hash Functions, Allocator Tuning, Journaling Control, and More; UBIFS Mount Options

collisions at some CPU cost. This may be used if EHASHCOLLISION errors are experienced with the r5 hash. r5 A modified version of the rupasov hash. It is used by default and is the best choice unless the filesystem has huge directories and unusual file-name patterns. detect Instructs mount to detect which hash function is in use by examining the filesystem being mounted, and to write this information into the reiserfs superblock. This is only useful on the first mount of an old format filesystem. hashed_relocation Tunes the block allocator. This may provide performance improvements in some situations. no_unhashed_relocation Tunes the block allocator. This may provide performance improvements in some situations. noborder Disable the border allocator algorithm invented by Yury Yu. Rupasov. This may provide performance improvements in some situations. nolog Disable journaling. This will provide slight performance improvements in some situations at the cost of losing reiserfs’s fast recovery from crashes. Even with this option turned on, reiserfs still performs all journaling operations, save for actual writes into its journaling area. Implementation of nolog is a work in progress. notail By default, reiserfs stores small files and 'file tails' directly into its tree. This confuses some utilities such as lilo(8). This option is used to disable packing of files into the tree. replayonly Replay the transactions which are in the journal, but do not actually mount the filesystem. Mainly used by reiserfsck. resize=number A remount option which permits online expansion of reiserfs partitions. Instructs reiserfs to assume that the device has number blocks. This option is designed for use with devices which are under logical volume management (LVM). There is a special resizer utility which can be obtained from ftp://ftp.namesys.com/pub/reiserfsprogs. user_xattr Enable Extended User Attributes. See the attr(1) manual page. acl Enable POSIX Access Control Lists. See the acl(5) manual page. barrier=none / barrier=flush This disables / enables the use of write barriers in the journaling code. barrier=none disables, barrier=flush enables (default). This also requires an IO stack which can support barriers, and if reiserfs gets an error on a barrier write, it will disable barriers 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. Mount options for ubifs UBIFS is a flash filesystem which works on top of UBI volumes. Note that atime is not supported and is always turned off. The device name may be specified as ubiX_Y UBI device number X, volume number Y ubiY UBI device number 0, volume number Y ubiX:NAME UBI device number X, volume with name NAME ubi:NAME UBI device number 0, volume with name NAME Alternative ! separator may be used instead of :. The following mount options are available: bulk_read Enable bulk-read. VFS read-ahead is disabled because it slows down the filesystem. Bulk-Read is an internal optimization. Some flashes may read faster if the data are read at

This section continues detailing Reiserfs mount options, including specific hash functions (`tea`, `r5`, `detect`), allocator tuning parameters (`hashed_relocation`, `no_unhashed_relocation`, `noborder`), journaling control (`nolog`), disabling file tail packing (`notail`), journal replay (`replayonly`), online resizing (`resize`), enabling extended user attributes (`user_xattr`), enabling POSIX ACLs (`acl`), and controlling write barriers (`barrier`). It then transitions to UBIFS mount options, describing the device naming conventions and available options such as `bulk_read`.