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