85 lines
2.8 KiB
Plaintext
85 lines
2.8 KiB
Plaintext
Subject: ANNOUNCE: mdadm 3.0-devel1 - A tool for managing Soft RAID under Linux
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I am pleased to announce the availability of
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mdadm version 3.0-devel1
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It is available at the usual places:
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countrycode=xx.
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http://www.${countrycode}kernel.org/pub/linux/utils/raid/mdadm/
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and via git at
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git://neil.brown.name/mdadm
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http://neil.brown.name/git?p=mdadm
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Note that this is a "devel" release. It is not intended for
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production use yet, but rather for testing and ongoing development.
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The significant change which justifies the new major version number is
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that mdadm can now handle metadata updates entirely in userspace.
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This allows mdadm to support metadata formats that the kernel knows
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nothing about.
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Currently two such metadata formats are supported:
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- DDF - The SNIA standard format
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- Intel Matrix - The metadata used by recent Intel ICH controlers.
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The manual pages have not yet been updated, but here is a brief outline.
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Externally managed metadata introduces the concept of a 'container'.
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A container is a collection of (normally) physical devices which have
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a common set of metadata. A container is assembled as an md array, but
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is left 'inactive'.
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A container can contain one or more data arrays. These are composed from
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slices (partitions?) of various devices in the container.
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For example, a 5 devices DDF set can container a RAID1 using the first
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half of two devices, a RAID0 using the first half of the remain 3 devices,
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and a RAID5 over thte second half of all 5 devices.
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A container can be created with
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mdadm --create /dev/md0 -e ddf -n5 /dev/sd[abcde]
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or "-e imsm" to use the Intel Matrix Storage Manager.
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An array can be created within a container either by giving the
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container name and the only member:
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mdadm -C /dev/md1 --level raid1 -n 2 /dev/md0
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or by listing the component devices
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mdadm -C /dev/md2 --level raid0 -n 3 /dev/sd[cde]
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The assemble a container, it is easiest just to pass each device in turn to
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mdadm -I
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for i in /dev/sd[abcde]
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do mdadm -I $i
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done
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This will assemble the container and the components.
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Alternately the container can be assembled explicitly
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mdadm -A /dev/md0 /dev/sd[abcde]
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Then the components can all be assembled with
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mdadm -I /dev/md0
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For each container, mdadm will start a program called "mdmon" which will
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monitor the array and effect any metadata updates needed. The array is
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initially assembled readonly. It is up to "mdmon" to mark the metadata
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as 'dirty' and which the array to 'read-write'.
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The version 0.90 and 1.x metadata formats supported by previous
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versions for mdadm are still supported and the kernel still performs
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the same updates it use to. The new 'mdmon' approach is only used for
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newly introduced metadata types.
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Any testing and feedback will be greatly appreciated.
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NeilBrown 18th September 2008
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