1*4882a593Smuzhiyun====== 2*4882a593Smuzhiyundm-ebs 3*4882a593Smuzhiyun====== 4*4882a593Smuzhiyun 5*4882a593Smuzhiyun 6*4882a593SmuzhiyunThis target is similar to the linear target except that it emulates 7*4882a593Smuzhiyuna smaller logical block size on a device with a larger logical block 8*4882a593Smuzhiyunsize. Its main purpose is to provide emulation of 512 byte sectors on 9*4882a593Smuzhiyundevices that do not provide this emulation (i.e. 4K native disks). 10*4882a593Smuzhiyun 11*4882a593SmuzhiyunSupported emulated logical block sizes 512, 1024, 2048 and 4096. 12*4882a593Smuzhiyun 13*4882a593SmuzhiyunUnderlying block size can be set to > 4K to test buffering larger units. 14*4882a593Smuzhiyun 15*4882a593Smuzhiyun 16*4882a593SmuzhiyunTable parameters 17*4882a593Smuzhiyun---------------- 18*4882a593Smuzhiyun <dev path> <offset> <emulated sectors> [<underlying sectors>] 19*4882a593Smuzhiyun 20*4882a593SmuzhiyunMandatory parameters: 21*4882a593Smuzhiyun 22*4882a593Smuzhiyun <dev path>: 23*4882a593Smuzhiyun Full pathname to the underlying block-device, 24*4882a593Smuzhiyun or a "major:minor" device-number. 25*4882a593Smuzhiyun <offset>: 26*4882a593Smuzhiyun Starting sector within the device; 27*4882a593Smuzhiyun has to be a multiple of <emulated sectors>. 28*4882a593Smuzhiyun <emulated sectors>: 29*4882a593Smuzhiyun Number of sectors defining the logical block size to be emulated; 30*4882a593Smuzhiyun 1, 2, 4, 8 sectors of 512 bytes supported. 31*4882a593Smuzhiyun 32*4882a593SmuzhiyunOptional parameter: 33*4882a593Smuzhiyun 34*4882a593Smuzhiyun <underyling sectors>: 35*4882a593Smuzhiyun Number of sectors defining the logical block size of <dev path>. 36*4882a593Smuzhiyun 2^N supported, e.g. 8 = emulate 8 sectors of 512 bytes = 4KiB. 37*4882a593Smuzhiyun If not provided, the logical block size of <dev path> will be used. 38*4882a593Smuzhiyun 39*4882a593Smuzhiyun 40*4882a593SmuzhiyunExamples: 41*4882a593Smuzhiyun 42*4882a593SmuzhiyunEmulate 1 sector = 512 bytes logical block size on /dev/sda starting at 43*4882a593Smuzhiyunoffset 1024 sectors with underlying devices block size automatically set: 44*4882a593Smuzhiyun 45*4882a593Smuzhiyunebs /dev/sda 1024 1 46*4882a593Smuzhiyun 47*4882a593SmuzhiyunEmulate 2 sector = 1KiB logical block size on /dev/sda starting at 48*4882a593Smuzhiyunoffset 128 sectors, enforce 2KiB underlying device block size. 49*4882a593SmuzhiyunThis presumes 2KiB logical blocksize on /dev/sda or less to work: 50*4882a593Smuzhiyun 51*4882a593Smuzhiyunebs /dev/sda 128 2 4 52