What is the limitation in AIX? Post: 302804009

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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

05-08-2013

Registered User

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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LEARN ABOUT BSD

go-packages

GO-PACKAGES(7)						 Miscellaneous Information Manual					    GO-PACKAGES(7)

NAME

       go - tool for managing Go source code

DESCRIPTION

       Many commands apply to a set of packages:

	     go action [packages]

       Usually, [packages] is a list of import paths.

       An  import path that is a rooted path or that begins with a . or .. element is interpreted as a file system path and denotes the package in
       that directory.

       Otherwise, the import path P denotes the package found in the directory DIR/src/P for some DIR listed in the  GOPATH  environment  variable
       (see 'go help gopath').

       If no import paths are given, the action applies to the package in the current directory.

       The  special  import path "all" expands to all package directories found in all the GOPATH trees.  For example, 'go list all' lists all the
       packages on the local system.

       The special import path "std" is like all but expands to just the packages in the standard Go library.

       An import path is a pattern if it includes one or more "..." wildcards, each of which can match any string, including the empty string  and
       strings	containing slashes.  Such a pattern expands to all package directories found in the GOPATH trees with names matching the patterns.
       As a special case, x/... matches x as well as x's subdirectories.  For example, net/... expands to net and packages in its subdirectories.

       An import path can also name a package to be downloaded from a remote repository.  Run 'go help remote' for details.

       Every package in a program must have a unique import path.  By convention, this is arranged by starting each path with a unique prefix that
       belongs	to  you.   For example, paths used internally at Google all begin with 'google', and paths denoting remote repositories begin with
       the path to the code, such as 'code.google.com/p/project'.

       As a special case, if the package list is a list of .go files from a single directory, the command is applied to a single synthesized pack-
       age made up of exactly those files, ignoring any build constraints in those files and ignoring any other files in the directory.

AUTHOR

       This manual page was written by Michael Stapelberg <stapelberg@debian.org>, for the Debian project (and may be used by others).

								    2012-05-13							    GO-PACKAGES(7)

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