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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
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ff_hfs(1M)																ff_hfs(1M)

NAME
ff_hfs: ff - list file names and statistics for HFS file system SYNOPSIS
num] num] inode-list] num] file] prefix] special ... DESCRIPTION
The command reads the i-list and directories of each special file special, assuming it to be an HFS file system, saving i-node data for files that match the selection criteria. Output consists of the path name for each saved i-node, plus any other file information requested using the print options below. Output fields are positional. The output is produced in i-node order; fields are separated by tabs. The default line produced by contains the path name and i-number fields. With all options specified, the output fields include path name, i- number, size, and user ID. The num parameter in the options descriptions is a decimal number, where means more than num, means less than num, and num means exactly num. A day is defined as a 24-hour period. lists only a single path name out of many possible ones for an i-node with more than one link, unless you specify the option. With applies no selection criteria to the names listed. All possible names for every linked file on the file system are included in the output. On very large file systems, memory may run out before completes execution. Options and Arguments recognizes the following options and arguments: Select a file if the i-node has been accessed in num days. Select a file if the i-node has been changed in num days. Specify the HFS file system type. Generate names for any i-node specified in the inode-list. Do not display the i-node number after each path name. Generate a list of all path names for files with more than one link. Select a file associated with an i-node if it has been modified in num days. Select a file associated with an i-node if it has been modified more recently than the specified file. Add the specified prefix to each path name. The default prefix is (dot). Write the file size, in bytes, after each path name. Write the owner's login name after each path name. 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. EXAMPLES
List the path names and i-numbers of all files in the file system Same as above, but suppress the printing of i-numbers: List files on the same file system that have been modified recently, displaying the path name, i-number, and owner's user name (the option). List only files that have been modified within the last two days (the option): List all files on the same file system, including the path name and i-number of each file, that was last accessed more than 30 days ago Find all path names associated with i-nodes and (the option): Execute the command on an HFS file system FILES
Static information about the file systems. SEE ALSO
find(1), ff(1M), ff_vxfs(1M), ncheck(1M), fstab(4). ff_hfs(1M)
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