| ====== | |
| 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 |