1 ====== 1 ======
2 dm-ebs 2 dm-ebs
3 ====== 3 ======
4 4
5 5
6 This target is similar to the linear target ex 6 This target is similar to the linear target except that it emulates
7 a smaller logical block size on a device with 7 a smaller logical block size on a device with a larger logical block
8 size. Its main purpose is to provide emulatio 8 size. Its main purpose is to provide emulation of 512 byte sectors on
9 devices that do not provide this emulation (i. 9 devices that do not provide this emulation (i.e. 4K native disks).
10 10
11 Supported emulated logical block sizes 512, 10 11 Supported emulated logical block sizes 512, 1024, 2048 and 4096.
12 12
13 Underlying block size can be set to > 4K to te 13 Underlying block size can be set to > 4K to test buffering larger units.
14 14
15 15
16 Table parameters 16 Table parameters
17 ---------------- 17 ----------------
18 <dev path> <offset> <emulated sectors> [<und 18 <dev path> <offset> <emulated sectors> [<underlying sectors>]
19 19
20 Mandatory parameters: 20 Mandatory parameters:
21 21
22 <dev path>: 22 <dev path>:
23 Full pathname to the underlying block- 23 Full pathname to the underlying block-device,
24 or a "major:minor" device-number. 24 or a "major:minor" device-number.
25 <offset>: 25 <offset>:
26 Starting sector within the device; 26 Starting sector within the device;
27 has to be a multiple of <emulated sect 27 has to be a multiple of <emulated sectors>.
28 <emulated sectors>: 28 <emulated sectors>:
29 Number of sectors defining the logical 29 Number of sectors defining the logical block size to be emulated;
30 1, 2, 4, 8 sectors of 512 bytes suppor 30 1, 2, 4, 8 sectors of 512 bytes supported.
31 31
32 Optional parameter: 32 Optional parameter:
33 33
34 <underlying sectors>: !! 34 <underyling sectors>:
35 Number of sectors defining the logical 35 Number of sectors defining the logical block size of <dev path>.
36 2^N supported, e.g. 8 = emulate 8 sect 36 2^N supported, e.g. 8 = emulate 8 sectors of 512 bytes = 4KiB.
37 If not provided, the logical block siz 37 If not provided, the logical block size of <dev path> will be used.
38 38
39 39
40 Examples: 40 Examples:
41 41
42 Emulate 1 sector = 512 bytes logical block siz 42 Emulate 1 sector = 512 bytes logical block size on /dev/sda starting at
43 offset 1024 sectors with underlying devices bl 43 offset 1024 sectors with underlying devices block size automatically set:
44 44
45 ebs /dev/sda 1024 1 45 ebs /dev/sda 1024 1
46 46
47 Emulate 2 sector = 1KiB logical block size on 47 Emulate 2 sector = 1KiB logical block size on /dev/sda starting at
48 offset 128 sectors, enforce 2KiB underlying de 48 offset 128 sectors, enforce 2KiB underlying device block size.
49 This presumes 2KiB logical blocksize on /dev/s 49 This presumes 2KiB logical blocksize on /dev/sda or less to work:
50 50
51 ebs /dev/sda 128 2 4 51 ebs /dev/sda 128 2 4
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