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L V M A Logical Volume Manager for Linux by Heinz Mauelshagen Sistina, Inc. <Mauelshagen@Sistina.com>

L V M A Logical Volume Manager for Linux by Heinz Mauelshagen Sistina, Inc. <Mauelshagen@Sistina.com>. Definition of the LVM. the Logical Volume Manager is a subsystem for on-line disk storage management

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L V M A Logical Volume Manager for Linux by Heinz Mauelshagen Sistina, Inc. <Mauelshagen@Sistina.com>

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  1. L V M A Logical Volume Manager for Linux by Heinz Mauelshagen Sistina, Inc. <Mauelshagen@Sistina.com>

  2. Definition of the LVM • the Logical Volume Manager is a subsystem for on-line disk storage management • it adds an additional layer to the i/o subsystem of the kernel to get a virtual view on disks • LVM enables you to deal with »virtual disks« and »virtual partitions« being fully online resizable and movable

  3. LVM Concept1 • usage of physical disks, disk partitions, multiple or loop devices as PVs(Physical Volumes; basic allocation device) • store metadata in so called VGDAs (Volume Group Descriptor Areas) on the PVs • group PVs in VGs (Volume Groups; »virtual disks«)

  4. LVM Concept2 • allocate VG storage to LVs (Logical Volumes; »virtual partitions«);basic units called PEs (Physical Extents) are mapped to their LEs (Logical Extents). • extend and reduce VGs and LVs online • use LVs like disks, disk partitions etc. for filesystems, databases etc. • access VGs and LVs via device special files named /dev/VolumeGroupName/*

  5. LVM Concept3 • build a command and a library layer to ease the integration of different or additional tools or graphical user interfaces • export and import VGs to bring them to or get them from different computer systems • support linear and striped (RAID0) LVs • support snapshot LVs

  6. 2 PVs Storage Architecture • 2 PVs

  7. PV PV VG Storage Architecture • VG with 2 PVs

  8. Storage Architecture • VG with 2 PVs and 1 LV PV PV VG LV

  9. Software Metrics1 • 99 VGs max • 256 LVs total (todays 8 bit minor #) in all VGs with ext2 (devfs tents to raise this) • 256 PVs total in one VG • up to 65534 PEs total per PV • up to 65534 LEs per LV • PE/LE sizes between several KB 8*) and GB • cabable of dealing with more than 1000 TB but limited by unsigned long variables in the Linux I/O subsystem on 32 bit platforms(128SCSI Ids*2TB*15 Partitions = 3b840TB)

  10. Upcomming Release • persistent snapshots • resizable snapshots • integration of LVM with the VFS to support atomic snapshot activation (reiserfs) • renaming of Volume Groups and Logical Volumes without deactivating them • devfs support

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