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Full Discussion: Why does ext3 allocate 8 blocks for files that are few bytes long
Operating Systems Linux Why does ext3 allocate 8 blocks for files that are few bytes long Post 302319587 by Tavo on Monday 25th of May 2009 10:45:16 PM
Old 05-25-2009
Why does ext3 allocate 8 blocks for files that are few bytes long
The title is clear: why does ext3 allocate 8 blocks for files that are few bytes long?
If I create a file named "test", put a few chars in it, and then I run:

Code:
stat test

I get that "Blocks: 8"

I searched in the web and found that ext does that, it allocates 8 blocks even if It doesn't need it. Fine by me, but what if, at some moment, I need that space? Will I get it?
If so, how does ext3 manage those semi-allocated blocks?
If not... well then, I think something is wrong here, giving 32KB to any small file as if hdd space were free seems stupid.

Could anyone enlighten me?
 

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LEARN ABOUT HPUX

df_nfs

df_hfs(1M)																df_hfs(1M)

NAME

       df_hfs: df - report number of free CDFS, HFS, or NFS file system disk blocks

SYNOPSIS

       FStype] specific_options] [special|directory]...

DESCRIPTION

       The  command  displays  the  number  of free 512-byte blocks and free inodes available for file systems by examining the counts kept in the
       superblock or superblocks.  If a special or a directory is not specified, the free space on all mounted file systems is displayed.  If  the
       arguments  to are path names, reports on the file systems containing the named files.  If the argument to is a special of an unmounted file
       system, the free space in the unmounted file system is displayed.

   Options
       recognizes the following options:

	      Report only the number of kilobytes (KB) free.

	      Report the total number of blocks allocated for swapping to the file system
			     as well as the number of blocks free for swapping to the file system.  This option is supported on HFS  file  systems
			     only.

	      Report the number of files free.

	      Report only the actual count of the blocks in the free list
			     (free inodes are not reported).  When this option is specified, reports on raw devices.

	      Report only on the
			     FStype  file  system  type  (see fstyp(1M)).  For the purposes of this manual entry, FStype can be one of and for the
			     CDFS, HFS, and NFS file systems, respectively.

	      Report the entire structure described in
			     statvfs(2).

	      Report the total number of inodes,
			     the number of free inodes, number of used inodes, and the percentage of inodes in use.

	      Report the allocation in kilobytes (KB).

	      Report on local file systems only.

	      Report the file system name.
			     If used with no other options, display a list of mounted file system types.

	      Specify options specific to the HFS file system type.
			     specific_options is a comma-separated list of suboptions.

			     The available suboption is:

				  Report the number of used and free inodes.

	      Report the total allocated block figures and the number of free blocks.

	      Report the percentage of blocks used,
			     the number of blocks used, and the number of blocks free.	This option cannot be used with other options.

	      Echo the completed command line, but perform 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.

       When  is used on an HFS file system, the file space reported is the space available to the ordinary user, and does not include the reserved
       file space specified by

       Unreported reserved blocks are available only to users who have appropriate privileges.	See tunefs(1M) for information about

       When is used on NFS file systems, the number of inodes is displayed as -1 .  This is due to superuser access restrictions over NFS.

EXAMPLES

       Report the number of free disk blocks for all mounted file systems:

       Report the number of free disk blocks for all mounted HFS file systems:

       Report the number of free files for all mounted NFS file systems:

       Report the total allocated block figures and the number of free blocks, for all mounted file systems:

       Report the total allocated block figures and the number of free blocks, for the file system mounted as /usr:

WARNINGS

       does not account for:

	      o  Disk space reserved for swap space,
	      o  Space used for the HFS boot block (8K bytes, 1 per file system),
	      o  HFS superblocks (8K bytes each, 1 per disk cylinder),
	      o  HFS cylinder group blocks (1K-8K bytes each, 1 per cylinder group),
	      o  Inodes (currently 128 bytes reserved for each inode).

       Non-HFS file systems may have other items that this command does not account for.

       The option, from prior releases, has been replaced by the option.

FILES

       File system devices.
       Static information about the file systems
       Mounted file system table

SEE ALSO

       du(1), df(1M), fsck(1M), fstab(4), fstyp(1M), statvfs(2), mnttab(4).

STANDARDS CONFORMANCE

																	df_hfs(1M)
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