1========= 2dm-stripe 3========= 4 5Device-Mapper's "striped" target is used to create a striped (i.e. RAID-0) 6device across one or more underlying devices. Data is written in "chunks", 7with consecutive chunks rotating among the underlying devices. This can 8potentially provide improved I/O throughput by utilizing several physical 9devices in parallel. 10 11Parameters: <num devs> <chunk size> [<dev path> <offset>]+ 12 <num devs>: 13 Number of underlying devices. 14 <chunk size>: 15 Size of each chunk of data. Must be at least as 16 large as the system's PAGE_SIZE. 17 <dev path>: 18 Full pathname to the underlying block-device, or a 19 "major:minor" device-number. 20 <offset>: 21 Starting sector within the device. 22 23One or more underlying devices can be specified. The striped device size must 24be a multiple of the chunk size multiplied by the number of underlying devices. 25 26 27Example scripts 28=============== 29 30:: 31 32 #!/usr/bin/perl -w 33 # Create a striped device across any number of underlying devices. The device 34 # will be called "stripe_dev" and have a chunk-size of 128k. 35 36 my $chunk_size = 128 * 2; 37 my $dev_name = "stripe_dev"; 38 my $num_devs = @ARGV; 39 my @devs = @ARGV; 40 my ($min_dev_size, $stripe_dev_size, $i); 41 42 if (!$num_devs) { 43 die("Specify at least one device\n"); 44 } 45 46 $min_dev_size = `blockdev --getsz $devs[0]`; 47 for ($i = 1; $i < $num_devs; $i++) { 48 my $this_size = `blockdev --getsz $devs[$i]`; 49 $min_dev_size = ($min_dev_size < $this_size) ? 50 $min_dev_size : $this_size; 51 } 52 53 $stripe_dev_size = $min_dev_size * $num_devs; 54 $stripe_dev_size -= $stripe_dev_size % ($chunk_size * $num_devs); 55 56 $table = "0 $stripe_dev_size striped $num_devs $chunk_size"; 57 for ($i = 0; $i < $num_devs; $i++) { 58 $table .= " $devs[$i] 0"; 59 } 60 61 `echo $table | dmsetup create $dev_name`; 62