summaryrefslogtreecommitdiff
path: root/Documentation/admin-guide/device-mapper/striped.rst
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/admin-guide/device-mapper/striped.rst')
-rw-r--r--Documentation/admin-guide/device-mapper/striped.rst61
1 files changed, 61 insertions, 0 deletions
diff --git a/Documentation/admin-guide/device-mapper/striped.rst b/Documentation/admin-guide/device-mapper/striped.rst
new file mode 100644
index 000000000000..e9a8da192ae1
--- /dev/null
+++ b/Documentation/admin-guide/device-mapper/striped.rst
@@ -0,0 +1,61 @@
+=========
+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`;