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Full Discussion: What is the limitation in AIX?
Operating Systems AIX What is the limitation in AIX? Post 302804009 by bakunin on Tuesday 7th of May 2013 11:55:12 PM
Old 05-08-2013
What DGPickett means is the following:

A directory is quite similar to a file and the bigger a file gets the longer it takes the system to read it, which is to be expected. Run a "grep" against a file of 10GB and it will take longer than against a file of 1k size.

Let us consider the case where you issue a command

Code:
grep regexp /path/to/some/file

What happens? Before "grep" can start its work the operating system has to find out which file to open. So it looks in the directory "/path/to/some" and searches there for the inode of "file". A "directory" now is nothing else than a (quite unsorted) list of file names and inode-numbers. The longer this list is the longer it will take the take the OS to search it and find the inode it is interested in.

Usually you won't notice even this difference because the OS uses otherwise unused parts of the memory to buffer such information. This is part of the "file system cache": the system won't read the directory information from disk, but use the copy it has already stored in memory. As memory is much faster than disk this will speed up things considerably. But as the directory gets bigger and bigger and memory is a limited resource at some point the list might not fit in memory any more additionally hurting the speed with which this list is searched.

Bottom line: even if there are no theoretical limits there is some practical limit to directory sizes. This practical limit is pushed as hardware gets faster and memory keeps getting bigger, disks getting faster, etc.., but it still remains.

To split a large directory there is no "standard tool" like there is "split" for files. Just create new directories and use "mv" to move files from one to the other. A command like

Code:
mv /path/to/file /other/path

will physically move a file only of the directories "/path/to" and "/other/path" are not part of the same filesystem. If they are it is simply a matter of removing the directory information from the one list and putting it into the other. It will take the same time regardless of file size, because the file itself is not touched, just "file metadata" - information about files instead of files themselves.

I hope this clears things up.

bakunin
These 2 Users Gave Thanks to bakunin For This Post:
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LEARN ABOUT HPUX

ncheck_hfs

ncheck_hfs(1M)															    ncheck_hfs(1M)

NAME

       ncheck_hfs: ncheck - generate a list of path names from inode numbers for a HFS file system

SYNOPSIS

       inode-numbers] [special ...]

DESCRIPTION

       when  invoked  without  arguments, generates a list of path names corresponding to the inode numbers of all files contained on the HFS file
       systems listed in If special is specified, ncheck reports on the special only.  Path names generated by are relative to the given  special.
       Names of directory files are followed by

   Options
	      Allow printing of the names
			     and which are ordinarily suppressed.

	      Specify the HFS file system type.

	      Report only on files whose inode numbers
			     are specified on the command line, in inode-numbers.  inode-numbers is a comma separated list of inode numbers.

	      Report only on special files
			     and regular files with set-user-ID mode.  The option is intended to discover concealed violations of security policy.

	      Echo the completed command line, but performs no other action.
			     The  command  line  is  generated by incorporating the user-specified options and other information derived from This
			     option allows the user to verify the command line.

	      Report only on files using sector numbers
			     specified on the command line in sector_ranges.  sector_ranges is a comma separated list of sector ranges.  A  sector
			     range is a starting sector number and an ending sector number separated by a dash, or just a sector number.  The sec-
			     tor numbers should be in DEV_BSIZE units.	If no pathname contains the sector number it will be reported as  free	or
			     containing file system structure. Sectors beyond the end of the file system will be reported as illegal.

   Access Control Lists
       Continuation  inodes  (that  is, inodes containing additional access control list information) are quietly skipped since they do not corre-
       spond to any path name.

EXAMPLES

       Execute the command on all special in

       Execute the command on HFS file system

EXTERNAL INFLUENCES

   International Code Set Support
       Single- and multi-byte character code sets are supported.

DIAGNOSTICS

       When the file system structure is improper, denotes the ``parent'' of a parentless file and a path-name beginning with denotes a loop.

AUTHOR

       was developed by AT&T and HP.

FILES

       Specifies the default file system type.
       Static information about the file systems.

SEE ALSO

       acl(5), fsck(1M), fstab(4), fs_wrapper(5), ncheck(1M), sort(1).

STANDARDS CONFORMANCE

																    ncheck_hfs(1M)
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