Partition Types

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Revision as of 16:26, 28 January 2009 by Grangerx (Talk | contribs)

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Arrays are built on top of block devices; typically disks.

This leads to 2 frequent questions:

  • Should I use entire device or a partition?
  • What partition type?

There is no right answer - you can choose.

Entire Devices or Partitions

Your editor prefers to use partitions that are slightly smaller than a device. This allows:

  • the device has a partition table - no 'partition table not found'
  • replacement disks even of the same model are often slightly smaller and making the partition 100Mb smaller than the device allows some tolerance.
  • no performance impact

Neil, the md/mdadm author, uses whole disks.

What Partition Type

If you are using partitions then there are only 2 sensible choices for your partition type:

  • 0xDA for non-fs data
  • 0xFD for old autodetect arrays

(From the mdadm 2.6.8 man-page) When creating partition-based arrays using mdadm and version-1.x superblocks, the partition type should be set to 0xDA (non fs-data). This type selection allows for greater precision since using any other type [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)], might create problems in the event of array recovery through a live cdrom.

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