Disk Volume Management

CSS-1

Terms

Extent – any contiguous set of clustersPartition – extent treated as a diskVolume - partition formatted with a file

systemBasic disk - basic volumes and logical

drivesDynamic disks

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WINDOWS

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Basic disk

Exists on single physical driveUses DOS partition tables

■ Simple volume (contiguous extents)■ Primary partitions■ Extended partitions■ Logical drives■ USB removable drives

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Dynamic disks (Windows)Simple volume ≈ primary partition or

logical driveOnly 1 user accessible partitionNot for bootable volumesUp to 1000 volumes on a systemRely on Logical Disk Manager (LDM)

and Virtual Disk ServiceAllows non-contiguous extents

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Dynamic disk volume types

Spanned volumesExtended volumesStriped volumesMirrored volumesRaid-5 volumes

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Partitions

Master Boot Record (DOS style) for Windows

■ 2 choices●4 primary partitions (maximum)●3 Primary + 1 extended partition

Globally Unique ID style■ Basic disk: Up to 128 primary partitions■ Dynamic disk: 1 LDM partition (like MBR)

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GUID

Allows partitions > 2 terabytesAdded reliability

■ Replication & CRC for partition table

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MBR example (Basic disk)

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1st Ptable entry

Master boot code

2nd Ptable entry

3rd Ptable entry

4th Ptable entry

Partition table

0x55AA

MBR

Primary Partition 1 C:

Primary Partition 2 E:

Primary Partition 3 F:

Logical Drive G::

Logical Drive H::

Extended Partition

Extended partition does NOT have to be last.Must be contiguous space.

Dynamic disk MBR

Similar to Basic MBR layoutNo extended partitionsOnly ONE Primary partition

■ Called the LDM partitionHidden partition at end for LDM DB

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Dynamic disk

Contains:●simple volumes●spanned volumes●striped volumes●mirrored volumes*●RAID-5 volumes*

* Depends on O/S version

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Dynamic Storage Terms

Simple vol: space on 1 diskSpanned vol: linked space on ≥ 1 disks

■ NOT fault tolerant■ CANNOT be mirrored

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LINUX

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A truism

On a Unix system, everything is either a file or a process.

Directories are just files with names of other files

Devices are treated as files with special attributes

http://en.wikipedia.org/wiki/Comparison_of_file_systems

CSS-14© 2012 D. J. Foreman

Partition management

Logical Volume Manager (kernel)Loaders

■ LILO (LInux boot LOader)■ GRUB (GRand Unified Boot loader)

Partitioning programs■ fdisk■ Gparted (Gnome partition editor)■ KDE Partition Manager

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Layout (from Wikipedia)

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PE=Physical Extent

Linux File Systems

Ext (1992)Ext2 (1993)- pref for SD & USBXFS (1994) – B-tree larger than its filesExt3 (1999) – journal, slow, htree index, max

filesystem size=32TBExt4 (2006) – max filesystem size=1 EB (1M TB)

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Htree indexing

Constant depth of 1 or 2 levelsHashes filenameNo rebalancing

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