diff options
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/00-INDEX | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/nilfs2.txt | 200 | ||||
| -rw-r--r-- | Documentation/filesystems/pohmelfs/design_notes.txt | 5 | ||||
| -rw-r--r-- | Documentation/filesystems/pohmelfs/info.txt | 21 | ||||
| -rw-r--r-- | Documentation/filesystems/vfs.txt | 3 |
5 files changed, 223 insertions, 8 deletions
diff --git a/Documentation/filesystems/00-INDEX b/Documentation/filesystems/00-INDEX index 52cd611..8dd6db7 100644 --- a/Documentation/filesystems/00-INDEX +++ b/Documentation/filesystems/00-INDEX @@ -68,6 +68,8 @@ ncpfs.txt - info on Novell Netware(tm) filesystem using NCP protocol. nfsroot.txt - short guide on setting up a diskless box with NFS root filesystem. +nilfs2.txt + - info and mount options for the NILFS2 filesystem. ntfs.txt - info and mount options for the NTFS filesystem (Windows NT). ocfs2.txt diff --git a/Documentation/filesystems/nilfs2.txt b/Documentation/filesystems/nilfs2.txt new file mode 100644 index 0000000..55c4300 --- /dev/null +++ b/Documentation/filesystems/nilfs2.txt @@ -0,0 +1,200 @@ +NILFS2 +------ + +NILFS2 is a log-structured file system (LFS) supporting continuous +snapshotting. In addition to versioning capability of the entire file +system, users can even restore files mistakenly overwritten or +destroyed just a few seconds ago. Since NILFS2 can keep consistency +like conventional LFS, it achieves quick recovery after system +crashes. + +NILFS2 creates a number of checkpoints every few seconds or per +synchronous write basis (unless there is no change). Users can select +significant versions among continuously created checkpoints, and can +change them into snapshots which will be preserved until they are +changed back to checkpoints. + +There is no limit on the number of snapshots until the volume gets +full. Each snapshot is mountable as a read-only file system +concurrently with its writable mount, and this feature is convenient +for online backup. + +The userland tools are included in nilfs-utils package, which is +available from the following download page. At least "mkfs.nilfs2", +"mount.nilfs2", "umount.nilfs2", and "nilfs_cleanerd" (so called +cleaner or garbage collector) are required. Details on the tools are +described in the man pages included in the package. + +Project web page: http://www.nilfs.org/en/ +Download page: http://www.nilfs.org/en/download.html +Git tree web page: http://www.nilfs.org/git/ +NILFS mailing lists: http://www.nilfs.org/mailman/listinfo/users + +Caveats +======= + +Features which NILFS2 does not support yet: + + - atime + - extended attributes + - POSIX ACLs + - quotas + - writable snapshots + - remote backup (CDP) + - data integrity + - defragmentation + +Mount options +============= + +NILFS2 supports the following mount options: +(*) == default + +barrier=on(*) This enables/disables barriers. barrier=off disables + it, barrier=on enables it. +errors=continue(*) Keep going on a filesystem error. +errors=remount-ro Remount the filesystem read-only on an error. +errors=panic Panic and halt the machine if an error occurs. +cp=n Specify the checkpoint-number of the snapshot to be + mounted. Checkpoints and snapshots are listed by lscp + user command. Only the checkpoints marked as snapshot + are mountable with this option. Snapshot is read-only, + so a read-only mount option must be specified together. +order=relaxed(*) Apply relaxed order semantics that allows modified data + blocks to be written to disk without making a + checkpoint if no metadata update is going. This mode + is equivalent to the ordered data mode of the ext3 + filesystem except for the updates on data blocks still + conserve atomicity. This will improve synchronous + write performance for overwriting. +order=strict Apply strict in-order semantics that preserves sequence + of all file operations including overwriting of data + blocks. That means, it is guaranteed that no + overtaking of events occurs in the recovered file + system after a crash. + +NILFS2 usage +============ + +To use nilfs2 as a local file system, simply: + + # mkfs -t nilfs2 /dev/block_device + # mount -t nilfs2 /dev/block_device /dir + +This will also invoke the cleaner through the mount helper program +(mount.nilfs2). + +Checkpoints and snapshots are managed by the following commands. +Their manpages are included in the nilfs-utils package above. + + lscp list checkpoints or snapshots. + mkcp make a checkpoint or a snapshot. + chcp change an existing checkpoint to a snapshot or vice versa. + rmcp invalidate specified checkpoint(s). + +To mount a snapshot, + + # mount -t nilfs2 -r -o cp=<cno> /dev/block_device /snap_dir + +where <cno> is the checkpoint number of the snapshot. + +To unmount the NILFS2 mount point or snapshot, simply: + + # umount /dir + +Then, the cleaner daemon is automatically shut down by the umount +helper program (umount.nilfs2). + +Disk format +=========== + +A nilfs2 volume is equally divided into a number of segments except +for the super block (SB) and segment #0. A segment is the container +of logs. Each log is composed of summary information blocks, payload +blocks, and an optional super root block (SR): + + ______________________________________________________ + | |SB| | Segment | Segment | Segment | ... | Segment | | + |_|__|_|____0____|____1____|____2____|_____|____N____|_| + 0 +1K +4K +8M +16M +24M +(8MB x N) + . . (Typical offsets for 4KB-block) + . . + .______________________. + | log | log |... | log | + |__1__|__2__|____|__m__| + . . + . . + . . + .______________________________. + | Summary | Payload blocks |SR| + |_blocks__|_________________|__| + +The payload blocks are organized per file, and each file consists of +data blocks and B-tree node blocks: + + |<--- File-A --->|<--- File-B --->| + _______________________________________________________________ + | Data blocks | B-tree blocks | Data blocks | B-tree blocks | ... + _|_____________|_______________|_____________|_______________|_ + + +Since only the modified blocks are written in the log, it may have +files without data blocks or B-tree node blocks. + +The organization of the blocks is recorded in the summary information +blocks, which contains a header structure (nilfs_segment_summary), per +file structures (nilfs_finfo), and per block structures (nilfs_binfo): + + _________________________________________________________________________ + | Summary | finfo | binfo | ... | binfo | finfo | binfo | ... | binfo |... + |_blocks__|___A___|_(A,1)_|_____|(A,Na)_|___B___|_(B,1)_|_____|(B,Nb)_|___ + + +The logs include regular files, directory files, symbolic link files +and several meta data files. The mata data files are the files used +to maintain file system meta data. The current version of NILFS2 uses +the following meta data files: + + 1) Inode file (ifile) -- Stores on-disk inodes + 2) Checkpoint file (cpfile) -- Stores checkpoints + 3) Segment usage file (sufile) -- Stores allocation state of segments + 4) Data address translation file -- Maps virtual block numbers to usual + (DAT) block numbers. This file serves to + make on-disk blocks relocatable. + +The following figure shows a typical organization of the logs: + + _________________________________________________________________________ + | Summary | regular file | file | ... | ifile | cpfile | sufile | DAT |SR| + |_blocks__|_or_directory_|_______|_____|_______|________|________|_____|__| + + +To stride over segment boundaries, this sequence of files may be split +into multiple logs. The sequence of logs that should be treated as +logically one log, is delimited with flags marked in the segment +summary. The recovery code of nilfs2 looks this boundary information +to ensure atomicity of updates. + +The super root block is inserted for every checkpoints. It includes +three special inodes, inodes for the DAT, cpfile, and sufile. Inodes +of regular files, directories, symlinks and other special files, are +included in the ifile. The inode of ifile itself is included in the +corresponding checkpoint entry in the cpfile. Thus, the hierarchy +among NILFS2 files can be depicted as follows: + + Super block (SB) + | + v + Super root block (the latest cno=xx) + |-- DAT + |-- sufile + `-- cpfile + |-- ifile (cno=c1) + |-- ifile (cno=c2) ---- file (ino=i1) + : : |-- file (ino=i2) + `-- ifile (cno=xx) |-- file (ino=i3) + : : + `-- file (ino=yy) + ( regular file, directory, or symlink ) + +For detail on the format of each file, please see include/linux/nilfs2_fs.h. diff --git a/Documentation/filesystems/pohmelfs/design_notes.txt b/Documentation/filesystems/pohmelfs/design_notes.txt index 6d6db60..dcf8335 100644 --- a/Documentation/filesystems/pohmelfs/design_notes.txt +++ b/Documentation/filesystems/pohmelfs/design_notes.txt @@ -56,9 +56,10 @@ workloads and can fully utilize the bandwidth to the servers when doing bulk data transfers. POHMELFS clients operate with a working set of servers and are capable of balancing read-only -operations (like lookups or directory listings) between them. +operations (like lookups or directory listings) between them according to IO priorities. Administrators can add or remove servers from the set at run-time via special commands (described -in Documentation/pohmelfs/info.txt file). Writes are replicated to all servers. +in Documentation/pohmelfs/info.txt file). Writes are replicated to all servers, which are connected +with write permission turned on. IO priority and permissions can be changed in run-time. POHMELFS is capable of full data channel encryption and/or strong crypto hashing. One can select any kernel supported cipher, encryption mode, hash type and operation mode diff --git a/Documentation/filesystems/pohmelfs/info.txt b/Documentation/filesystems/pohmelfs/info.txt index 4e3d501..db2e413 100644 --- a/Documentation/filesystems/pohmelfs/info.txt +++ b/Documentation/filesystems/pohmelfs/info.txt @@ -1,6 +1,8 @@ POHMELFS usage information. -Mount options: +Mount options. +All but index, number of crypto threads and maximum IO size can changed via remount. + idx=%u Each mountpoint is associated with a special index via this option. Administrator can add or remove servers from the given index, so all mounts, @@ -52,16 +54,27 @@ mcache_timeout=%u Usage examples. -Add (or remove if it already exists) server server1.net:1025 into the working set with index $idx +Add server server1.net:1025 into the working set with index $idx with appropriate hash algorithm and key file and cipher algorithm, mode and key file: -$cfg -a server1.net -p 1025 -i $idx -K $hash_key -k $cipher_key +$cfg A add -a server1.net -p 1025 -i $idx -K $hash_key -k $cipher_key Mount filesystem with given index $idx to /mnt mountpoint. Client will connect to all servers specified in the working set via previous command: mount -t pohmel -o idx=$idx q /mnt -One can add or remove servers from working set after mounting too. +Change permissions to read-only (-I 1 option, '-I 2' - write-only, 3 - rw): +$cfg A modify -a server1.net -p 1025 -i $idx -I 1 + +Change IO priority to 123 (node with the highest priority gets read requests). +$cfg A modify -a server1.net -p 1025 -i $idx -P 123 +One can check currect status of all connections in the mountstats file: +# cat /proc/$PID/mountstats +... +device none mounted on /mnt with fstype pohmel +idx addr(:port) socket_type protocol active priority permissions +0 server1.net:1026 1 6 1 250 1 +0 server2.net:1025 1 6 1 123 3 Server installation. diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt index deeeed0..f49eecf 100644 --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt @@ -277,8 +277,7 @@ or bottom half). unfreeze_fs: called when VFS is unlocking a filesystem and making it writable again. - statfs: called when the VFS needs to get filesystem statistics. This - is called with the kernel lock held + statfs: called when the VFS needs to get filesystem statistics. remount_fs: called when the filesystem is remounted. This is called with the kernel lock held |
