migrate - Move a file or file pages to another volume in
an AdvFS file domain
/usr/sbin/migrate [-p pageoffset] [-n pagecount] [-s volumeindex]
[-d volumeindex] filename
Specifies the volume index number of the volume to which
the pages are to be migrated. You can determine the volume
index number of the volumes in an AdvFS file domain by
using the showfile -x command. If you do not specify the
-d option, the AdvFS determines the destination of the
file or the file pages. The AdvFS moves the file or the
file pages to any volume or volumes with available space.
Specifies the number of pages to migrate, starting at the
pageoffset value. The default page count is to EOF. If
you do not specify the -n option, the migrate command
migrates pages from the pageoffset value to the end of the
file. Specifies the page offset of the first page to
migrate. The first page of the file is page 0. The default
page offset is 0. If you do not specify the -p option,
the migrate command migrates pages starting at page 0 of
the file. Specifies the volume index number of the volume
from which the pages are to be migrated. Use the showfile
-x command to determine the volume index number of the
volumes in an AdvFS file domain.
If you specify the -s option and the volume that
contains the file does not contain any data extents
of that file, the utility returns success without
taking any action.
You must use the -s option when you are migrating
striped files. You can move pages of a striped file
or a stripe file segment, which is the entire portion
of a striped file that resides on the specified
volume, to another volume.
Specifies the name of the file or file pages to be
migrated from the volume. The file can be simple or
striped.
The migrate utility moves the specified simple (unstriped)
file to another volume in the same file domain. The utility
also moves pages of a simple file or pages of a
striped file segment to another volume (or volumes, if
necessary) within the file domain.
There are no read/write restrictions when using this command,
you can migrate a file while users are reading it,
writing to it, or both. When direct I/O is enabled, the
migrate operation may experience interrupts. In all other
cases the migrate operation executes without disrupting
file I/O.
When you run the migrate utility with only the -p and -n
options, the utility attempts to allocate destination
pages contiguously on one destination volume in the file
domain. If there are not enough free, contiguous blocks
to accomplish the move, the utility then attempts to allocate
the pages to the next available blocks on the same
volume. If there are not enough free blocks on the same
volume, the utility then attempts to moves the file to the
next available volume or volumes. The utility returns an
error diagnostic if it cannot accomplish the move.
You must use the -s, -n, and -p options in order to move
pages of a striped file from one volume to another. Only
those pages assigned to the source volume are moved to the
destination volume: all pages in the file are not moved.
You can use the migrate utility to move heavily accessed
files or pages of files to a different volume in the file
domain. Use the -d option to indicate a specific volume.
Also, you can use the utility to defragment a specific
file, because the migrate utility defragments a file whenever
possible.
The migrate utility does not evaluate your migration decisions.
As a result, you can move more than one striped
file segment onto the same volume, which can defeat the
purpose of striping the file.
The number of stripes is determined by the number of
extent maps for the file although a map may point to more
than one volume. If you want to change the number of
stripes for the file, you must re-create the file with the
desired number of stripes.
You can only perform one migrate operation on the same
file at the same time. When you migrate a striped file,
you can only migrate from one source volume at a time.
You must be the root user to use this utility.
The utility returns a value of 0 (zero) on success, otherwise
it returns a nonzero value and an error diagnostic.
The following examples perform tasks using the migrate
utility. To migrate the simple file abc from its current
volume to any other volume in the file domain, enter: #
migrate abc To migrate the simple file abc from volume 1
of a file domain to volume 6 of a file domain, enter: #
migrate -s 1 -d 6 abc To migrate pages 10 through 99 (that
is, 90 pages starting at page 10) of the simple file abc
from its current volume to volume 2 of the file domain,
enter: # migrate -p 10 -n 90 -d 2 abc The following example
migrates all the pages of a file that reside on a
specified volume. A file, stripe_1, is striped across Volumes
1, 2, and 3 of a six-volume AdvFS file domain. To
migrate the entire stripe file segment of the stripe_1
file that is on volume 1 to volume 4 of the domain, enter:
# migrate -s 1 -d 4 stripe_1 The following example moves
some, but not all, file pages on one volume of a striped
file to another volume in the file domain. Use the showfile
command with the -x flag to determine the volume
index, the page count, and the page offset for the volume.
Then specify the pages you want to migrate.
In this example the file str_file is striped across
three volumes (1, 2, and 3) of a four volume
file domain. To move some of the pages from volume
2 to volume 4, first identify the page offset and
the page count for the pages you want to move: #
showfile -x str_file
Id Vol PgSz Pages XtntType Segs SegSz I/O
Perf File 6.8007 2 16 123 stripe 3 8
async 69% str_file
extentMap: 1
pageOff pageCnt volIndex volBlock
blockCnt
0 8 3 67312
624
24 8
48 8
72 8
96 7
103 1 3 67952
64
120 3
extentCnt: 2
extentMap: 2
pageOff pageCnt volIndex volBlock
blockCnt
8 8 4 67312
352
32 8
56 6
62 2 4 67696
64
80 2
82 6 4 67856
96
104 8 4 68080
128
extentCnt: 4
extentMap: 3
pageOff pageCnt volIndex volBlock
blockCnt
16 8 1 76048
256
40 8
64 8 1 76320
128
88 8 1 76544
128
112 8 1 76720
128
extentCnt: 4
The showfile output shows that volume 4, as shown
in extent map 2, contains a total of 40 pages of
the striped file starting at page offset 8. You
want to migrate the first 16 pages that reside on
volume 4 to volume 2. The first eight pages to be
moved start at page offset 8 and end at page offset
15. The next eight pages to be moved start at page
offset 32 and end at page offset 39. So the range
of pages you want to move (the value of the -n
flag) is 32 pages; that is, 8 to 39 inclusive.
(The other pages in the range are on other volumes
because the file is striped.) The command will
migrate only the pages from the specified volume in
the specified range. # migrate -p 8 -n 32 -s 4 -d
2 str_file
Because you did not move all of the pages from volume
4 to volume 2, the file is now stored on four
volumes. Note, that this does not change the
stripe width of the file. There are still three
extent maps.
To confirm the migration, reissue the showfile command.
Following is part of the output showing the
new extent map 2:
extentMap: 2
pageOff pageCnt volIndex volBlock
blockCnt
8 8 2 51920
256
32 8
56 8 4 68592
256
80 8
104 8 4 68080
128
extentCnt: 4
Commands: showfdmn(8), showfile(8), stripe(8)
Files: advfs(4)
migrate(8)
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