| ====== |
| 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: |
| |
| <underyling 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 |
