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========= 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`; |