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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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FLS(1)							      General Commands Manual							    FLS(1)

NAME
fls - List file and directory names in a disk image. SYNOPSIS
fls [-adDFlpruvV] [-m mnt ] [-z zone ] [-f fstype ] [-s seconds ] [-i imgtype ] [-o imgoffset ] [-b dev_sector_size] image [images] [ inode ] DESCRIPTION
fls lists the files and directory names in the image and can display file names of recently deleted files for the directory using the given inode. If the inode argument is not given, the inode value for the root directory is used. For example, on an NTFS file system it would be 5 and on a Ext3 file system it would be 2. The arguments are as follows: -a Display the "." and ".." directory entries (by default it does not) -d Display deleted entries only -D Display directory entries only -f fstype The type of file system. Use '-f list' to list the supported file system types. If not given, autodetection methods are used. -F Display file (all non-directory) entries only. -l Display file details in long format. The following contents are displayed: file_type inode file_name mod_time acc_time chg_time cre_time size uid gid -m mnt Display files in time machine format so that a timeline can be created with mactime(1). The string given as mnt will be prepended to the file names as the mounting point (for example /usr). -p Display the full path for each entry. By default it denotes the directory depth on recursive runs with a '+' sign. -r Recursively display directories. This will not follow deleted directories, because it can't. -s seconds The time skew of the original system in seconds. For example, if the original system was 100 seconds slow, this value would be -100. This is only used if -l or -m are given. -i imgtype Identify the type of image file, such as raw or split. Use '-i list' to list the supported types. If not given, autodetection methods are used. -o imgoffset The sector offset where the file system starts in the image. -b dev_sector_size The size, in bytes, of the underlying device sectors. If not given, the value in the image format is used (if it exists) or 512-bytes is assumed. -u Display undeleted entries only -v Verbose output to stderr. -V Display version. -z zone The ASCII string of the time zone of the original system. For example, EST or GMT. These strings must be defined by your operating system and may vary. image [images] One (or more if split) disk or partition images whose format is given with '-i'. Once the inode has been determined, the file can be recovered using icat(1) from The Coroners Toolkit. The amount of information recovered from deleted file entries varies depending on the system. For example, on Linux, a recently deleted file can be easily recovered, while in Solaris not even the inode can be determined. If you just want to find what file name belongs to an inode, it is easier to use ffind(1). EXAMPLES
To get a list of all files and directories in an image use: # fls -r image 2 or just (if no inode is specified, the root directory inode is used): # fls -r image To get the full path of deleted files in a given directory: # fls -d -p image 29 To get the mactime output do: # fls -m /usr/local image 2 If you have a disk image and the file system starts in sector 63, use: # fls -o 63 disk-img.dd If you have a disk image that is split use: # fls -i "split" -o 63 disk-1.dd disk-2.dd disk-3.dd SEE ALSO
ffind(1), icat(1) AUTHOR
Brian Carrier <carrier at sleuthkit dot org> Send documentation updates to <doc-updates at sleuthkit dot org> FLS(1)
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