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Commands Reference, Volume 2
fileplace Command
Purpose
Displays the placement of file blocks within logical
or physical volumes.
Syntax
fileplace [ { -l | -p } [ -i ] [ -v ]
] File | [-m LogicalVolumeName]
Description
The fileplace command displays
the placement of a specified file within the logical or physical volumes containing
the file.
By default, the fileplace command
lists to standard output the ranges of logical volume fragments allocated
to the specified file. The order in which the logical volume fragments are
listed corresponds directly to their order in the file. A short header indicates
the file size (in bytes), the name of the logical volume in which the file
lies, the block size (in bytes) for that volume, the fragment size in bytes,
and the compression, indicating if the file system is compressed or not.
Occasionally, portions of a file may not be mapped
to any fragments in the volume. These areas, whose size is an integral number
of fragments, are implicitly zero-filled by the file system. The fileplace command indicates which areas in a file have no allocated fragments.
Optionally, the fileplace command
also displays:
- Statistics indicating the degree to which
the file is spread within the volume.
- The indirect block addresses for the file.
- The file's placement on physical (as opposed
to logical) volume, for each of the physical copies of the file.
Notes:
- The fileplace command is not able to display the
placement of remote Network File System (NFS) files. If a remote file is specified,
the fileplace command returns an error message. However,
the placement of the remote file can be displayed if the fileplace command is run directly on the file server.
- The fileplace command reads the file's list of blocks
directly from the logical volume on disk. If the file is newly created, extended,
or truncated, the file system information may not yet be on the disk when
the fileplace command is run. Use the sync command to flush the file information to the logical
volume.
- There is no Indirect/Double Indirect blocks concept in JFS2 filesystem.
The file is represented in terms of extents. Therefore the size of the maximum
extent depends on the aggregate block size. With a 512 byte aggregate block
size (the smallest allowable), the maximum extent is 512*(2^ 24-1) bytes long
(slightly under 8G). With a 4096 byte aggregate block size (the largest allowable),
the maximum extent is 4096*(2^ 24-1) bytes long (slightly under 64G).
These
limits apply only to a single extent; in no way do they have any limiting
effects on overall file sizes.
Flags
-i |
Displays the indirect blocks for the file, if any. The indirect blocks
are displayed in terms of either their logical or physical volume block addresses,
depending on whether the -l or -p flag
is specified. |
-l |
Displays file placement in terms of logical volume fragments, for the
logical volume containing the file. The -l and -p flags are mutually exclusive.
Note:
If neither the -l flag nor the-p flag
is specified, the -l flag is implied by default. If
both flags are specified, the -p flag is used. |
-m LogicalVolumeName |
Displays the logical to physical map for a logical
volume. |
-p |
Displays file placement in terms of underlying physical volume, for
the physical volumes that contain the file. If the logical volume containing
the file is mirrored, the physical placement is displayed for each mirror
copy. The -l and -p flags are
mutually exclusive. |
-v |
Displays more information about the file and its placement, including
statistics on how widely the file is spread across the volume and the degree
of fragmentation in the volume. The statistics are expressed in terms of either
the logical or physical volume fragment numbers, depending on whether the -l or -p flag is specified.
File space efficiency is calculated as the number of nonnull
fragments (N) divided by the range of fragments (R) assigned to the file and multiplied by 100, or (N /R) x 100. Range is calculated
as the highest assigned address minus the lowest assigned address plus 1,
or MaxBlk-MinBlk+1. For example,
the logical blocks written for the file are 01550 through 01557, so N equals 8. The range, R, (01557 - 01550 +1)
also equals 8. Space efficiency for this file is 100% or 8/8 x 100. The -v flag message prints the results of the (N/R)+100 equation.
According to this
method of calculating efficiency, files greater than 32KB are never 100% efficient
because of their use of the indirect block.
Sequential
efficiency is defined as 1 minus the number of gaps (nG) divided by number of possible gaps (nPG)
or 1 - (nG/nPG). The number
of possible gaps equals N minus 1 ( nPG=N - 1). If the file is written to 9 blocks (greater than 32KB), and
the logical fragment column shows:
01550-01557
01600
The file is stored in 2 fragments out of a possible 9 fragments.
The sequential efficiency calculation for this file is:
nG=1
nPG=9-1=8
(1-1/8) x 100=87.5% |
Examples
- To display the placement of a file in its
logical volume, enter:
fileplace data1
This example displays
the list of fragments and the logical volume that contains the file data1.
- To display the indirect blocks for a file,
enter:
fileplace -i data1
In addition to the default list of
logical volume fragments, the indirect blocks (if any) used to store the file
block addresses in the file system are enumerated.
- To display more placement information for
a file, enter:
fileplace -v data1
In addition to the default
list of logical volume fragments, statistics about the placement efficiency
are displayed.
- To display all information about the placement
of a file on its physical volumes, enter:
fileplace -piv data1
This
example displays the list of file and indirect blocks in terms of the underlying
physical volumes, and includes statistics about the efficiency of the placement.
Files
/dev/hd0, /dev/hd1, .../dev/hdn |
Specifies the logical volume. |
Related Information
The sync command.
Monitoring and Tuning Disk
I/O in AIX 5L Version 5.2 Performance Management Guide.
The Logical Volume Storage
Overview inAIX 5L Version 5.2 System Management Concepts: Operating System and Devices defines and discusses logical
volume storage.
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