Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 |
Mikulas Patocka | f14fa69 | 2012-07-27 15:08:00 +0100 | [diff] [blame^] | 19 | be a multiple of the chunk size multiplied by the number of underlying devices. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 20 | |
| 21 | |
| 22 | Example scripts |
| 23 | =============== |
| 24 | |
| 25 | [[ |
| 26 | #!/usr/bin/perl -w |
| 27 | # Create a striped device across any number of underlying devices. The device |
| 28 | # will be called "stripe_dev" and have a chunk-size of 128k. |
| 29 | |
| 30 | my $chunk_size = 128 * 2; |
| 31 | my $dev_name = "stripe_dev"; |
| 32 | my $num_devs = @ARGV; |
| 33 | my @devs = @ARGV; |
| 34 | my ($min_dev_size, $stripe_dev_size, $i); |
| 35 | |
| 36 | if (!$num_devs) { |
| 37 | die("Specify at least one device\n"); |
| 38 | } |
| 39 | |
| 40 | $min_dev_size = `blockdev --getsize $devs[0]`; |
| 41 | for ($i = 1; $i < $num_devs; $i++) { |
| 42 | my $this_size = `blockdev --getsize $devs[$i]`; |
| 43 | $min_dev_size = ($min_dev_size < $this_size) ? |
| 44 | $min_dev_size : $this_size; |
| 45 | } |
| 46 | |
| 47 | $stripe_dev_size = $min_dev_size * $num_devs; |
| 48 | $stripe_dev_size -= $stripe_dev_size % ($chunk_size * $num_devs); |
| 49 | |
| 50 | $table = "0 $stripe_dev_size striped $num_devs $chunk_size"; |
| 51 | for ($i = 0; $i < $num_devs; $i++) { |
| 52 | $table .= " $devs[$i] 0"; |
| 53 | } |
| 54 | |
| 55 | `echo $table | dmsetup create $dev_name`; |
| 56 | ]] |
| 57 | |