52 lines
1.6 KiB
ReStructuredText
52 lines
1.6 KiB
ReStructuredText
======
|
|
dm-ebs
|
|
======
|
|
|
|
|
|
This target is similar to the linear target except that it emulates
|
|
a smaller logical block size on a device with a larger logical block
|
|
size. Its main purpose is to provide emulation of 512 byte sectors on
|
|
devices that do not provide this emulation (i.e. 4K native disks).
|
|
|
|
Supported emulated logical block sizes 512, 1024, 2048 and 4096.
|
|
|
|
Underlying block size can be set to > 4K to test buffering larger units.
|
|
|
|
|
|
Table parameters
|
|
----------------
|
|
<dev path> <offset> <emulated sectors> [<underlying sectors>]
|
|
|
|
Mandatory parameters:
|
|
|
|
<dev path>:
|
|
Full pathname to the underlying block-device,
|
|
or a "major:minor" device-number.
|
|
<offset>:
|
|
Starting sector within the device;
|
|
has to be a multiple of <emulated sectors>.
|
|
<emulated sectors>:
|
|
Number of sectors defining the logical block size to be emulated;
|
|
1, 2, 4, 8 sectors of 512 bytes supported.
|
|
|
|
Optional parameter:
|
|
|
|
<underlying sectors>:
|
|
Number of sectors defining the logical block size of <dev path>.
|
|
2^N supported, e.g. 8 = emulate 8 sectors of 512 bytes = 4KiB.
|
|
If not provided, the logical block size of <dev path> will be used.
|
|
|
|
|
|
Examples:
|
|
|
|
Emulate 1 sector = 512 bytes logical block size on /dev/sda starting at
|
|
offset 1024 sectors with underlying devices block size automatically set:
|
|
|
|
ebs /dev/sda 1024 1
|
|
|
|
Emulate 2 sector = 1KiB logical block size on /dev/sda starting at
|
|
offset 128 sectors, enforce 2KiB underlying device block size.
|
|
This presumes 2KiB logical blocksize on /dev/sda or less to work:
|
|
|
|
ebs /dev/sda 128 2 4
|