340 likes | 602 Views
Disk Volume Management. Terms. Extent – any contiguous set of clusters Partition – extent treated as a disk Volume - partition formatted with a file system Basic disk - basic volumes and logical drives Dynamic disks. Windows. Basic disk. Exists on single physical drive
E N D
Terms • Extent – any contiguous set of clusters • Partition – extent treated as a disk • Volume - partition formatted with a file system • Basic disk - basic volumes and logical drives • Dynamic disks
Basic disk • Exists on single physical drive • Uses DOS partition tables • Simple volume (contiguous extents) • Primary partitions • Extended partitions • Logical drives • USB removable drives
Dynamic disks (Windows) • Simple volume ≈ primary partition or logical drive • Only 1 user accessible partition • Not for bootable volumes • Up to 1000 volumes on a system • Rely on Logical Disk Manager (LDM) and Virtual Disk Service • Allows non-contiguous extents
Dynamic disk volume types • Spanned volumes • Extended volumes • Striped volumes • Mirrored volumes • Raid-5 volumes
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)
GUID • Allows partitions > 2 terabytes • Added reliability • Replication & CRC for partition table
MBR example (Basic disk) Master boot code 1st Ptable entry Partition table 2ndPtable entry MBR 3rdPtable entry 4thPtable entry 0x55AA Primary Partition 1 C: Primary Partition 2 E: Primary Partition 3 F: Logical Drive G:: Extended Partition Logical Drive H:: Extended partition does NOT have to be last. Must be contiguous space.
Dynamic disk MBR • Similar to Basic MBR layout • No extended partitions • Only ONE Primary partition • Called the LDM partition • Hidden partition at end for LDM DB
Dynamic disk • Contains: • simple volumes • spanned volumes • striped volumes • mirrored volumes* • RAID-5 volumes* * Depends on O/S version
Dynamic Storage Terms • Simple vol: space on 1 disk • Spanned vol: linked space on ≥ 1 disks • NOT fault tolerant • CANNOT be mirrored
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
Partition management • Logical Volume Manager (kernel) • Loaders • LILO (LInux boot LOader) • GRUB (GRandUnified Boot loader) • Partitioning programs • fdisk • Gparted(Gnome partition editor) • KDE Partition Manager
Layout (from Wikipedia) PE=Physical Extent
Linux File Systems • Ext (1992) • Ext2 (1993)- pref for SD & USB • XFS (1994) – B-tree larger than its files • Ext3 (1999) – journal, slow, htreeindex, max filesystemsize=32TB • Ext4 (2006) – max filesystemsize=1 EB (1M TB)
Htree indexing • Constant depth of 1 or 2 levels • Hashes filename • No rebalancing