Logical Volume Manager. An Introduction
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LVM (Logical Volume Manager) allows managing disks in a different way by creating virtual disks called logical volumes from physical partitions. It does not have the same limitations as physical disks. LVM concepts include physical volumes representing physical partitions, volume groups which act as virtual disks by combining multiple physical volumes, and logical volumes which are partitions within volume groups that can be resized and moved independently of physical storage. LVM provides flexibility in managing storage and can be used with other technologies like encryption and RAID.
Logical Volume Manager. An Introduction
- 1. Logical Volume Manager An Introduction
- 2. Logical Volume Manager What is? LVM (Logical Volume Manager) allows to manage disks in a different way: creates one or more virtual disks with virtual partitions, from physical partitions No limited by physical disk
- 3. Logical Volume Manager What is? LVM (Logical Volume Manager) allows to manage disks in a different way: creates one or more virtual disks with virtual partitions, from physical partitions No limited by physical disk
- 4. Logical Volume Manager Concepts Physical Volume (PV) : physical partition from real disk Volume Group (VG) : like a virtual disk Logical Volume (LV) : a partition in a Volume Group Physical Extent (PE) : like a 'cluster' in PV Logical Extent (LE) : like a 'cluster' in LV
- 5. Logical Volume Manager Concepts Create one or more VG from one or more PV, and then create LVs in each VG VG /dev/sda1 /dev/vg/lv1 /dev/sda2 /dev/vg/lv2 /dev/vg/lv3
- 6. Logical Volume Manager PVs pvcreate: creates a PV pvremove: removes a PV pvdisplay: shows information about a PV pvscan: scan all PVs in the system pvck: check a PV for errors (1) Create one or more partitions with fdisk, with type LVM (2) pvcreate /dev/<partition>
- 7. Logical Volume Manager VGs vgcreate: creates a VG vgremove: removes a VG vgextend: extend a VG with more PVs vgreduce: drops PVs from a VG vgdisplay: shows info about VG vgscan: scan for all VGs in system vgchange: change VG properties vgck, vgexport, vgmerge, vgsplit, vgrename
- 8. Logical Volume Manager VGs (1) Create one or more partitions with fdisk, with type LVM (2) pvcreate /dev/sda1 (3) pvcreate /dev/hdb2 (4) pvcreate /dev/hdc3 (5) vgcreate myvg /dev/sda1 /dev/hdb2 /dev/hdc3
- 9. Logical Volume Manager LVs lvcreate: creates a LV lvremove: removes a LV lvscan: scan for all LVs in a system lvdisplay: shows info about a LV lvrename, lvresize, lvreduce, lvchange
- 10. Logical Volume Manager LVs (1) Create a VG (2) lvcreate -L<size> -n <name> <vg> lvcreate -L10G -n mylv myvg It creates /dev/myvg/mylv (a link to /dev/mapper/myvg-mylv ) mkfs.ext3 /dev/myvg/mylv
- 11. Logical Volume Manager Snapshots A snapshot is an image of a LV Created instantly Read-only / read-write (LVM2) lvcreate -s -L<size> -n <name> <lv> RW: lvcreate -s -L1G -n mylv-snapshot /dev/myvg/mylv RO: lvcreate -s -L1G -n mylv-snapshot -p r /dev/myvg/mylv
- 12. Logical Volume Manager Snapshots Snapshot is like a 'pointer' to the same data in original LV Each time data in original LV is modified (or in snapshot if it was created as RW), a copy is done previously in exception table When it becomes full it is automatically disabled
- 13. Logical Volume Manager Uses of Snapshots To test: create snapshots and then use them as the main partitions If you don't like something, revert to original and drop the snapshots To backup: use a snapshot to create backups This way, you can continue to work while backuping is done, without a problem of having an inconsistency lvcreate -s -L1G -n snaproot /dev/vg/lvroot run-backup.sh /dev/vg/snaproot lvremove -f /dev/vg/snaproot
- 14. Logical Volume Manager LVM and other technologies /dev/* /dev/mapper/* /dev/* /dev/* /dev/md0 LUKS RAID
- 15. Logical Volume Manager LVM and other technologies /dev/* /dev/mapper/* /dev/* /dev/vg/* /dev/* /dev/* /dev/vg/* LUKS LVM
- 16. Logical Volume Manager LVM and other technologies /dev/* /dev/vg/* /dev/vg/* LUKS LVM
- 17. Logical Volume Manager LVM and other technologies /dev/vg/* /dev/* /dev/mapper/* LUKS LVM
- 18. Logical Volume Manager LVM and other technologies /dev/vg/* /dev/vg/* /dev/* /dev/* LUKS LVM RAID
- 19. Logical Volume Manager LVM and other technologies /dev/* /dev/* /dev/* /dev/vg1/* /dev/* /dev/* /dev/* /dev/vg2/* /dev/vg3/* /dev/vg3/* LUKS LUKS LVM LVM LVM
- 20. Logical Volume Manager My Laptop /dev/sdaA tmp home swap sbox root var music /dev/sdaB /dev/sdaC LUKS VG-CRYPT VG-UNCRYPT
- 21. Logical Volume Manager The End That's all, folks!