Kirk McKusick baa12a84a7 The purpose of this change to the FFS layout policy is to reduce the ... running time for a full fsck. It also reduces the random access time for large files and speeds the traversal time for directory tree walks. The key idea is to reserve a small area in each cylinder group immediately following the inode blocks for the use of metadata, specifically indirect blocks and directory contents. The new policy is to preferentially place metadata in the metadata area and everything else in the blocks that follow the metadata area. The size of this area can be set when creating a filesystem using newfs(8) or changed in an existing filesystem using tunefs(8). Both utilities use the `-k held-for-metadata-blocks' option to specify the amount of space to be held for metadata blocks in each cylinder group. By default, newfs(8) sets this area to half of minfree (typically 4% of the data area). This work was inspired by a paper presented at Usenix's FAST '13: www.usenix.org/conference/fast13/ffsck-fast-file-system-checker Details of this implementation appears in the April 2013 of ;login: www.usenix.org/publications/login/april-2013-volume-38-number-2. A copy of the April 2013 ;login: paper can also be downloaded from: www.mckusick.com/publications/faster_fsck.pdf. Reviewed by: kib Tested by: Peter Holm MFC after: 4 weeks		2013-03-22 21:45:28 +00:00
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ffs	The purpose of this change to the FFS layout policy is to reduce the	2013-03-22 21:45:28 +00:00
ufs	When renaming a directory from one parent directory to another,	2013-03-20 17:57:00 +00:00