Based on kernel version 2.6.26. Page generated on 2008-07-16 21:12 EST.
1 dm-stripe 2 ========= 3 4 Device-Mapper's "striped" target is used to create a striped (i.e. RAID-0) 5 device across one or more underlying devices. Data is written in "chunks", 6 with consecutive chunks rotating among the underlying devices. This can 7 potentially provide improved I/O throughput by utilizing several physical 8 devices in parallel. 9 10 Parameters: <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 18 One or more underlying devices can be specified. The striped device size must 19 be a multiple of the chunk size and a multiple of the number of underlying 20 devices. 21 22 23 Example 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 31 my $chunk_size = 128 * 2; 32 my $dev_name = "stripe_dev"; 33 my $num_devs = @ARGV; 34 my @devs = @ARGV; 35 my ($min_dev_size, $stripe_dev_size, $i); 36 37 if (!$num_devs) { 38 die("Specify at least one device\n"); 39 } 40 41 $min_dev_size = `blockdev --getsize $devs[0]`; 42 for ($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 $chunk_size"; 52 for ($i = 0; $i < $num_devs; $i++) { 53 $table .= " $devs[$i] 0"; 54 } 55 56 `echo $table | dmsetup create $dev_name`; 57 ]]