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/Documentation/device-mapper/striped.txt

https://bitbucket.org/evzijst/gittest
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 1dm-stripe
 2=========
 3
 4Device-Mapper's "striped" target is used to create a striped (i.e. RAID-0)
 5device across one or more underlying devices. Data is written in "chunks",
 6with consecutive chunks rotating among the underlying devices. This can
 7potentially provide improved I/O throughput by utilizing several physical
 8devices in parallel.
 9
10Parameters: <num devs> <chunk size> [<dev path> <offset>]+
11    <num devs>: Number of underlying devices.
12    <chunk size>: Size of each chunk of data. Must be a power-of-2 and at
13                  least as large as the system's PAGE_SIZE.
14    <dev path>: Full pathname to the underlying block-device, or a
15                "major:minor" device-number.
16    <offset>: Starting sector within the device.
17
18One or more underlying devices can be specified. The striped device size must
19be a multiple of the chunk size and a multiple of the number of underlying
20devices.
21
22
23Example scripts
24===============
25
26[[
27#!/usr/bin/perl -w
28# Create a striped device across any number of underlying devices. The device
29# will be called "stripe_dev" and have a chunk-size of 128k.
30
31my $chunk_size = 128 * 2;
32my $dev_name = "stripe_dev";
33my $num_devs = @ARGV;
34my @devs = @ARGV;
35my ($min_dev_size, $stripe_dev_size, $i);
36
37if (!$num_devs) {
38        die("Specify at least one device\n");
39}
40
41$min_dev_size = `blockdev --getsize $devs[0]`;
42for ($i = 1; $i < $num_devs; $i++) {
43        my $this_size = `blockdev --getsize $devs[$i]`;
44        $min_dev_size = ($min_dev_size < $this_size) ?
45                        $min_dev_size : $this_size;
46}
47
48$stripe_dev_size = $min_dev_size * $num_devs;
49$stripe_dev_size -= $stripe_dev_size % ($chunk_size * $num_devs);
50
51$table = "0 $stripe_dev_size striped $num_devs $chunk_size";
52for ($i = 0; $i < $num_devs; $i++) {
53        $table .= " $devs[$i] 0";
54}
55
56`echo $table | dmsetup create $dev_name`;
57]]
58