linux/Documentation/device-mapper/striped.txt
Michael Witten 95f21c5c6d Documentation/device-mapper: s/getsize/getsz/
According to `man blockdev':

  --getsize
         Print device size (32-bit!) in sectors.
         Deprecated in favor of the --getsz option.
  ...
  --getsz
         Get size in 512-byte sectors.

Hence, occurrences of `--getsize' should be replaced with `--getsz',
which this commit has achieved as follows:

  $ cd "$repo"
  $ git grep -l -e --getsz
  Documentation/device-mapper/delay.txt
  Documentation/device-mapper/dm-crypt.txt
  Documentation/device-mapper/linear.txt
  Documentation/device-mapper/log-writes.txt
  Documentation/device-mapper/striped.txt
  Documentation/device-mapper/switch.txt
  $ cd Documentation/device-mapper
  $ sed -i s/getsize/getsz/g *

Signed-off-by: Michael Witten <mfwitten@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2016-12-14 10:54:27 +01:00

58 lines
1.8 KiB
Plaintext

dm-stripe
=========
Device-Mapper's "striped" target is used to create a striped (i.e. RAID-0)
device across one or more underlying devices. Data is written in "chunks",
with consecutive chunks rotating among the underlying devices. This can
potentially provide improved I/O throughput by utilizing several physical
devices in parallel.
Parameters: <num devs> <chunk size> [<dev path> <offset>]+
<num devs>: Number of underlying devices.
<chunk size>: Size of each chunk of data. Must be at least as
large as the system's PAGE_SIZE.
<dev path>: Full pathname to the underlying block-device, or a
"major:minor" device-number.
<offset>: Starting sector within the device.
One or more underlying devices can be specified. The striped device size must
be a multiple of the chunk size multiplied by the number of underlying devices.
Example scripts
===============
[[
#!/usr/bin/perl -w
# Create a striped device across any number of underlying devices. The device
# will be called "stripe_dev" and have a chunk-size of 128k.
my $chunk_size = 128 * 2;
my $dev_name = "stripe_dev";
my $num_devs = @ARGV;
my @devs = @ARGV;
my ($min_dev_size, $stripe_dev_size, $i);
if (!$num_devs) {
die("Specify at least one device\n");
}
$min_dev_size = `blockdev --getsz $devs[0]`;
for ($i = 1; $i < $num_devs; $i++) {
my $this_size = `blockdev --getsz $devs[$i]`;
$min_dev_size = ($min_dev_size < $this_size) ?
$min_dev_size : $this_size;
}
$stripe_dev_size = $min_dev_size * $num_devs;
$stripe_dev_size -= $stripe_dev_size % ($chunk_size * $num_devs);
$table = "0 $stripe_dev_size striped $num_devs $chunk_size";
for ($i = 0; $i < $num_devs; $i++) {
$table .= " $devs[$i] 0";
}
`echo $table | dmsetup create $dev_name`;
]]