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% Registration dmraid - device-mapper RAID tool
% [2]Register/Submit Proposal Heinz Mauelshagen (heinzm@redhat.com)
Device-mapper, the new Linux 2.6 kernel
generic device-mapping facility, is capable of
mapping block devices in various ways (e.g.
linear, striped, mirrored). The mappings are
implemented in runtime loadable plugins called
mapping targets.
These mappings can be used to support
arbitrary software RAID solutions on Linux
2.6, such as ATARAID, without the need to have
a special low-level driver as it used to be
with Linux 2.4. This avoids code-redundancy
and reduces error rates.
Device-mapper runtime mappings (eg, map sector
N of a mapped device onto sector M of another
device) are defined in mapping tables.
The dmraid application is capable of creating
these for a variety of ATARAID solutions (eg.
Highpoint, NVidia, Promise, VIA). It uses an
abstracted representation of RAID devices and
RAID sets internally to keep properties such
as paths, sizes, offsets into devices and
layout types (e.g., RAID0). RAID sets can be of
arbitrary hierarchical depth in order to
reflect more complex RAID configurations such
as RAID10.
Because the various vendor specific metadata
formats stored onto ATA devices by the ATARAID
BIOS are all different, metadata format
handlers are used to translate between the
ondisk representation and the internal
abstracted format.
The mapping tables which need to be loaded
into device-mapper managed devices are derived
from the internal abstracted format.
My talk will give a device-mapper
architecture/feature overview and elaborate on
the dmraid architecture and how it uses the
device-mapper features to enable access to
ATARAID devices.
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