460 lines
13 KiB
Markdown
460 lines
13 KiB
Markdown
---
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title: Howto LVM
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category: linux disk
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...
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* <http://www.tldp.org/HOWTO/LVM-HOWTO/>
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LVM est un système permettant de gérer des « logical volumes » (LV) indépendamment des disques.
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On obtient ainsi un système de partitionnement plus souple, cela facilite notamment l'augmentation (future) de la taille d'un LV.
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## Installation
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~~~
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# apt install lvm2
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~~~
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### PV : les partitions LVM
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On doit ensuite créer des partitions de type « Linux LVM » (code `8E`).
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Puis on initialise les partitions pour LVM :
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~~~
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# pvcreate /dev/hda1
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# pvcreate /dev/hdb1
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~~~
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**Note** : dans certains cas, on devra utiliser l'option `-ff` (par exemple pour réinitialiser une partition)
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On pourra ainsi lister les partitions LVM du système avec `pvdisplay` ou `pvs` :
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~~~
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# pvdisplay
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--- Physical volume ---
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PV Name /dev/hda1
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VG Name group1
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PV Size 124.84 GB / not usable 1.52 MB
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Allocatable yes
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PE Size (KByte) 4096
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Total PE 31959
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Free PE 7639
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Allocated PE 24320
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PV UUID T12qj5-SEkv-zNrB-QUdG-tFua-b6ok-p1za3e
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--- Physical volume ---
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PV Name /dev/hdb1
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VG Name group1
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PV Size 13.08 GB / not usable 2.08 MB
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Allocatable yes
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PE Size (KByte) 4096
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Total PE 3347
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Free PE 3347
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Allocated PE 0
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PV UUID CQEeDw-TYNK-n0nh-G7ti-3U3J-4zgk-a7xg2S
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# pvs
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PV VG Fmt Attr PSize PFree
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/dev/hda1 group1 lvm2 a- 13.07G 13.07G
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/dev/hdb1 group1 lvm2 a- 124.84G 34.84G
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# pvs -o pv_mda_count,pv_mda_free /dev/hda1
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#PMda #PMdaFree
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1 91.50K
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# pvscan
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PV /dev/sda9 VG group1 lvm2 [124.84 GB / 29.84 GB free]
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PV /dev/sda12 VG group1 lvm2 [13.07 GB / 13.07 GB free]
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Total: 2 [137.91 GB] / in use: 2 [137.91 GB] / in no VG: 0 [0 ]
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~~~
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Si la partition est redimensionnée, on peut augmenter la taille du PV :
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~~~
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# pvresize /dev/hda1
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~~~
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### VG : les groupes de volumes
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Une fois nos PV initialisés, on créé un ou plusieurs groupes de volumes (VG) dans lesquels on découpera les volumes logiques (LV).
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~~~
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# vgcreate group1 /dev/hda1 /dev/hdb1
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Volume group "mylvmtest" successfully created
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~~~
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On peut ainsi les lister avec les commandes `vgdisplay` ou `vgs` :
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~~~
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# vgdisplay
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--- Volume group ---
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VG Name group1
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System ID
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Format lvm2
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Metadata Areas 2
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Metadata Sequence No 28
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VG Access read/write
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VG Status resizable
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MAX LV 0
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Cur LV 5
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Open LV 4
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Max PV 0
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Cur PV 2
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Act PV 2
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VG Size 137.91 GB
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PE Size 4.00 MB
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Total PE 35306
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Alloc PE / Size 24320 / 95.00 GB
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Free PE / Size 10986 / 42.91 GB
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VG UUID zwApn7-SCSx-ju4h-6Y1R-x6ie-3wl0-uSE1DE
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# vgs
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VG #PV #LV #SN Attr VSize VFree
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group1 2 5 0 wz--n- 137.91G 42.91G
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# vgscan
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Reading all physical volumes. This may take a while...
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Found volume group "group1" using metadata type lvm2
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~~~
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### LV : les volumes logiques
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On peut maintenant découper nos volumes finaux :
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~~~
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# lvcreate -L5G -nfirstlvmvol group1
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Logical volume "firstlvmvol" created
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# lvcreate -L10G -nsecondlvmvol group1
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Logical volume "secondlvmvol" created
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~~~
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On a ainsi des périphériques de stockage utilisables (accessibles via `/dev/mapper/<VG>-<LV>` ou `/dev/<VG>/<LV>`) que l'on peut formater :
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~~~
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# mkfs.ext4 /dev/mapper/group1-firstlvmvol
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# mkfs.ext4 /dev/group1/secondlvmvol
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~~~
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On peut lister les LV avec `lvdisplay` ou `lvs` :
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~~~
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# lvdisplay
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--- Logical volume ---
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LV Name /dev/group1/firstlvmvol
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VG Name group1
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LV UUID iHCvHy-ow0G-Idf2-hNOi-TRFe-BqvW-tmowLj
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LV Write Access read/write
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LV Status available
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# open 1
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LV Size 5.00 GB
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Current LE 2560
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Segments 1
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Allocation inherit
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Read ahead sectors auto
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- currently set to 256
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Block device 253:0
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--- Logical volume ---
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LV Name /dev/group1/secondlvmvol
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VG Name group1
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LV UUID S5GPY7-7q6n-1FCy-ydKA-Js2e-BAOy-wlgYQO
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LV Write Access read/write
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LV Status available
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# open 1
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LV Size 10.00 GB
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Current LE 12800
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Segments 1
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Allocation inherit
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Read ahead sectors auto
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- currently set to 256
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Block device 253:1
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# lvs
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LV VG Attr LSize Origin Snap% Move Log Copy% Convert
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firstlvmvol group1 -wi-ao 5.00G
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secondlvmvol group1 -wi-ao 10.00G
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# lvscan
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ACTIVE '/dev/group1/firstlvmvol' [5.00 GB] inherit
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ACTIVE '/dev/group1/secondlvmvol' [10.00 GB] inherit
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~~~
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### Les snapshots LVM
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Un snapshot LVM sert à « figer » une partition à chaud. Cela permettra de faire une vraie sauvegarde « tranquillement » par la suite.
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Exemple typique, une base SQL stocke ses fichiers dans `/srv/sql` qui est en LVM :
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* On arrête la base SQL (ou on la « lock »)
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* On déclenche un snapshot LVM de `/srv/sql`
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* On redémarre (ou « délock ») la base SQL : elle n'aura été arrêtée que quelques secondes !
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* Ensuite, on peut monter le snapshot et faire tranquillement son backup (tar, dd, rsync, etc.)
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* On peut enfin supprimer le snapshot vu qu'il ne sera plus présent au prochain boot
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**Note** : il semble qu'on peut pas trop avoir deux snapshots en même temps.
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~~~
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# lvcreate -L100M -s -n snap /dev/mylvmtest/firstlvmvol
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Logical volume "snap" created
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# lvdisplay
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--- Logical volume ---
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LV Name /dev/mylvmtest/firstlvmvol
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VG Name mylvmtest
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LV UUID 4vOXer-YH8x-AB9T-3MoP-BESB-7fyn-ce0Rho
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LV Write Access read/write
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LV snapshot status source of
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/dev/mylvmtest/snap [active]
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LV Status available
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# open 0
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LV Size 500.00 MB
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Current LE 125
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Segments 1
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Allocation inherit
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Read ahead sectors 0
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Block device 253:0
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--- Logical volume ---
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LV Name /dev/mylvmtest/snap
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VG Name mylvmtest
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LV UUID lF0wn9-7O3A-FacC-gnVM-SPwE-fCnI-5jb9wz
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LV Write Access read/write
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LV snapshot status active destination for /dev/mylvmtest/firstlvmvol
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LV Status available
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# open 0
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LV Size 500.00 MB
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Current LE 125
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COW-table size 100.00 MB
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COW-table LE 25
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Allocated to snapshot 0.02%
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Snapshot chunk size 8.00 KB
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Segments 1
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Allocation inherit
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Read ahead sectors 0
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Block device 253:3
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# mkdir /tmp/snap
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# mount /dev/mylvmtest/snap /tmp/snap/
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# lvcreate -L100M -s -n snap2 /dev/mylvmtest/firstlvmvol
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Logical volume "snap2" created
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device-mapper: snapshots: Invalidating snapshot: Unable to allocate exception.
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Buffer I/O error on device dm-3, logical block 530
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lost page write due to I/O error on dm-3
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Buffer I/O error on device dm-3, logical block 530
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lost page write due to I/O error on dm-3
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Buffer I/O error on device dm-3, logical block 530
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lost page write due to I/O error on dm-3
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Buffer I/O error on device dm-3, logical block 1
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lost page write due to I/O error on dm-3
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Buffer I/O error on device dm-3, logical block 1
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lost page write due to I/O error on dm-3
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# umount /tmp/snap
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# lvremove /dev/mylvmtest/snap
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Do you really want to remove active logical volume "snap"? [y/n]: y
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Logical volume "snap" successfully removed
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~~~
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### LVM mirror : du RAID1 avec LVM
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Une fonctionnalité peu connue de LVM est de permettre de faire du RAID1.
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Peu d'intérêt à part peut-être gérer du RAID1 « retaillable » sans gérer une couche « MDADM + LVM ».
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~~~
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# pvcreate /dev/sda7
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Physical volume "/dev/sda7" successfully created
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# pvcreate /dev/sdb5
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Physical volume "/dev/sdb5" successfully created
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# lvcreate -L180G -m1 -nlvmirror --corelog vg00 /dev/sda7 /dev/sdb5
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Logical volume "lvmirror" created
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# lvs -a
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LV VG Attr LSize Origin Snap% Move Log Copy%
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lvmirror vg00 mwi-ao 180.00G 8.60
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[lvmirror_mimage_0] vg00 iwi-ao 180.00G
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[lvmirror_mimage_1] vg00 iwi-ao 180.00G
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~~~
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Pour étendre un miroir LVM, on ajoute des PV au VG :
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~~~
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# pvcreate /dev/sda8
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Physical volume "/dev/sda8" successfully created
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# pvcreate /dev/sdb6
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Physical volume "/dev/sdb6" successfully created
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# vgextend vg00 /dev/sda8 /dev/sdb6
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Volume group "vg00" successfully extended
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~~~
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On désactive le miroir, on retaille, on réactive :
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~~~
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# lvextend -L+25G /dev/vg00/lvmirror
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Extending 2 mirror images.
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Mirrors cannot be resized while active yeta.
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# umount /dev/vg00/lvmirror
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# lvchange -an /dev/vg00/lvmirror
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# lvextend -L+25G /dev/vg00/lvmirror
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Extending 2 mirror images.
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Extending logical volume lvmirror to 205.00 GB
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Logical volume lvmirror successfully resized
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# lvchange -ay /dev/vg00/lvmirror
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~~~
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Enfin on retaille le filesystem :
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~~~
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# e2fsck -f /dev/vg00/lvmirror
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e2fsck 1.40-WIP (14-Nov-2006)
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Pass 1: Checking inodes, blocks, and sizes
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Pass 2: Checking directory structure
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Pass 3: Checking directory connectivity
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Pass 4: Checking reference counts
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Pass 5: Checking group summary information
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/dev/vg00/lvmirror: 216749/23592960 files (13.5% non-contiguous), 44825506/47185920 blocks
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# resize2fs /dev/vg00/lvmirror
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resize2fs 1.40-WIP (14-Nov-2006)
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Resizing the filesystem on /dev/vg00/lvmirror to 53739520 (4k) blocks.
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The filesystem on /dev/vg00/lvmirror is now 53739520 blocks long.
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~~~
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## FAQ
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### Supprimer une partition LVM d'un VG
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~~~
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# pvmove -v /dev/hde1
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Finding volume group "mylvmtest"
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Archiving volume group "mylvmtest" metadata.
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Creating logical volume pvmove0
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mirror: Required device-mapper target(s) not detected in your kernel
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# vgreduce mylvmtest /dev/hde1
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Removed "/dev/hde1" from volume group "mylvmtest"
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~~~
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### Supprimer un LV
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~~~
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# lvremove -v /dev/testlvm/testlvm2
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Using logical volume(s) on command line
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Do you really want to remove active logical volume "testlvm2"? [y/n]: y
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Archiving volume group "testlvm" metadata.
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Found volume group "testlvm"
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Removing testlvm-testlvm2
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Found volume group "testlvm"
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Releasing logical volume "testlvm2"
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Creating volume group backup "/etc/lvm/backup/testlvm"
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Logical volume "testlvm2" successfully removed
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~~~
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### Augmenter la taille d'un LV
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~~~
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# umount /dev/mylvmtest/thirdlvmvol
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# lvextend -L+1G /dev/mylvmtest/thirdlvmvol
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Extending logical volume thirdlvmvol to 4,00 GB
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Logical volume thirdlvmvol successfully resized
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# resize2fs -p /dev/mylvmtest/thirdlvmvol
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# e2fsck -f /dev/mylvmtest/thirdlvmvol -C0
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e2fsck 1.35 (28-Feb-2004)
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Passe 1: vérification inodes, blocs, et des tailles
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Passe 2: vérification de la structure répertoire
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Passe 3: vérification de lca connectivité répertoire
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Pass 4: vérification des compteur de références
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Pass 5: vérification de l'information du sommaire groupe
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/dev/mylvmtest/thirdlvmvol: 11/393216 fichier (0.0% non
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blocs
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# resize2fs -p /dev/mylvmtest/thirdlvmvol
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resize2fs 1.35 (28-Feb-2004)
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Resizing the filesystem on /dev/mylvmtest/thirdlvmvol to
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Le système de fichiers /dev/mylvmtest/thirdlvmvol a main
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8576 blocs.
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~~~
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### Réduire la taille d'un LV
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~~~
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ACTIVE '/dev/mylvmtest/secondlvmvol' [60,00 GB] inherit
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# umount /dev/mylvmtest/secondlvmvol
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# e2fsck -f /dev/mylvmtest/secondlvmvol -C0
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# resize2fs /dev/mylvmtest/secondlvmvol 50G
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resize2fs 1.41.12 (17-May-2010)
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Resizing the filesystem on /dev/mylvmtest/secondlvmvol to 13107200 (4k) blocks.
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The filesystem on /dev/mylvmtest/secondlvmvol is now 13107200 blocks long.
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# lvreduce -L-10G /dev/mylvmtest/secondlvmvol
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WARNING: Reducing active logical volume to 50,00 GB
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THIS MAY DESTROY YOUR DATA (filesystem etc.)
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Do you really want to reduce secondlvmvol? [y/n]: y
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Reducing logical volume secondlvmvol to 50,00 GB
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Logical volume secondlvmvol successfully resized
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# mount /dev/mylvmtest/secondlvmvol
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~~~
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### LVM et les tailles
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Les tailles reportées par LVM sont très peu fiables.
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Un exemple concret avec un VG qui annonce :
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~~~
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VG Size 137.91 GB
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PE Size 4.00 MB
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Total PE 35306
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Alloc PE / Size 23040 / 90.00 GB
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Free PE / Size 12266 / 47.91 GB
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~~~
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On a tendance à croire qu'il reste de la place… Pourtant un `lvextend` ou `lvcreate` échoue.
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Par exemple :
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~~~
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# lvextend -L+10G /dev/group1/data
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Extending logical volume data to 30.00 GB
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device-mapper: resume ioctl failed: Invalid argument
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Unable to resume group1-data (253:3)
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Logical volume data successfully resized
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# lvcreate -L5G -ntest group1
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device-mapper: resume ioctl failed: Invalid argument
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Unable to resume group1-test (253:4)
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/dev/group1/test: write failed after 0 of 4096 at 0: No space left on device
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Logical volume "test" created
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~~~
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### Restauration
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**/!\\ à manipuler avec beaucoup de précautions /!\\**
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LVM sauvegarde ses métadatas dans `/etc/lvm/backup` et `/etc/lvm/archive`.
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On peut éventuellement les restaurer via la commande `vgcfgrestore`.
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### Infos sur les volumes
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~~~
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# dmestup info -c
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# dmestup info
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~~~ |