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sys_attrs_ufs(5)					      sys_attrs_ufs(5)

NAME
       sys_attrs_ufs - ufs subsystem attributes

DESCRIPTION
       This  reference	page  lists and describes attributes for the UNIX File
       System  (ufs) kernel subsystem. Refer  to  the  sys_attrs(5)  reference
       page for an introduction to the topic of kernel subsystem attributes.

	      A	 value	that  enables (1) or disables (0) the creation of fast
	      symbolic link files.

	      Default value: 1 (enabled)

	      A value that enables (1) or disables (0) the  delaying  of  full
	      write  buffer  flushing  to disk at the next sync call. Enabling
	      this attribute might adversely affect real-time workload perfor‐
	      mance.

	      Default value: 0 (disabled)

	      Size  of (number of slots in) the inode hash chain table for the
	      inode least recently used (LRU) cache.

	      Default value: 2048 (slots)

	      Minimum value: 64

	      Maximum value:  1,073,741,824

	      Large inode hash chain tables spread the	inode  structures  and
	      may  make chain lengths short. In general, chains should contain
	      only 2 or 3 elements.   This  can	 reduce	 linear	 searches  and
	      improve	lookup	speeds.	 Therefore,  ncreasing	the  value  of
	      inode_hash_size can improve performance but requires  more  mem‐
	      ory;  values closer to the maximum are recommended only for Very
	      Large Memory (VLM) systems.

	      Obsolete.	 This attribute has been replaced by the  vfs  subsys‐
	      tem's  max_ufs_mounts  attribute,	 which is tunable at run time.
	      See sys_attrs_vfs(5) for information about max_ufs_mounts.

	      The range of blocks behind the current  block  location  through
	      which  to	 search	 for  a free block to allocate for an indirect
	      block write operation (for all writes other than the  first).  A
	      value greater than 1 enables a look-behind search before writing
	      each indirect block after the first block write operation.

	      Default value: 16 (blocks)

	      Minimum value: 1

	      Maximum value: 64

	      The maximum number of vnodes that UFS can process while flushing
	      dirty buffers on the mount list before releasing the lock on the
	      mount list to other components.  If  ufs_lockholdmax  number  of
	      vnodes  is  reached  before  all dirty buffers on all vnodes are
	      flushed from the mount list, UFS releases the  mount  list  lock
	      and  regains  it	later  to process (flush dirty buffers on) the
	      remaining vnodes.

	      Default value: 500 (vnodes)

	      Minimum value: 0 (means that UFS must  release  the  mount  list
	      lock each time a vnode is processed)

	      Maximum value: 5000

	      Reducing the value of ufs_lockholdmax can improve system respon‐
	      siveness for systems under  heavy	 I/O  load.  The  cost	is  an
	      increase in CPU overhead (more time required to flush dirty buf‐
	      fers from the mount list). Reducing  the	ufs_lockholdmax	 value
	      too  low	or  on	systems	 with low I/O overhead incurs CPU cost
	      without increasing system responsiveness.

	      If the rt_preempt_opt attribute is set, ufs_lockholdmax is auto‐
	      matically	 reduced to 50 to better support the strict preemption
	      requirements of realtime operations.

	      A value that enables (nonzero) or disables (0) an operation that
	      restricts	 how  blocks  of  stale UFS data and metadata (such as
	      inodes) are reused. When ufs_object_safety is set to  a  nonzero
	      value,  blocks  are  cleared  before  being rewritten and update
	      operations are ordered in a certain way to conform to  C2	 secu‐
	      rity  requirements.  For example, during file creation, a dinode
	      is always written before a directory entry is updated  to	 point
	      to  that	dinode. When a file is deleted, the directory entry is
	      always updated before the dinode is deleted.

	      Default value: 0 (disabled)

	      Change ufs_object_safety to a nonzero value only if a  C2	 secu‐
	      rity  level is a system requirement. There is a serious UFS per‐
	      formance cost associated	with  this  change.  Furthermore,  the
	      default  setting,	 even though not in strict conformance with C2
	      security requirements, leaves a low probability  that  confiden‐
	      tial data will be exposed.

SEE ALSO
       sys_attrs(5)

							      sys_attrs_ufs(5)
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