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选题[tech]: 20210922 Add storage with LVM
sources/tech/20210922 Add storage with LVM.md
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sources/tech/20210922 Add storage with LVM.md
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[#]: subject: "Add storage with LVM"
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[#]: via: "https://opensource.com/article/21/9/add-storage-lvm"
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[#]: author: "Ayush Sharma https://opensource.com/users/ayushsharma"
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[#]: collector: "lujun9972"
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[#]: translator: " "
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[#]: reviewer: " "
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[#]: publisher: " "
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[#]: url: " "
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Add storage with LVM
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======
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LVM enables extreme flexibility in how you configure your storage.
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![Storage units side by side][1]
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Logical Volume Manager (LVM) allows for a layer of abstraction between the operating system and the hardware. Normally, your OS looks for disks (`/dev/sda`, `/dev/sdb`, and so on) and partitions within those disks (`/dev/sda1`, `/dev/sdb1`, and so on).
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In LVM, a virtual layer is created between the operating system and the disks. Instead of one drive holding some number of partitions, LVM creates a unified storage pool (called a _Volume Group_) that spans any number of physical drives (called _Physical Volumes_). Using the storage available in a Volume Group, LVM provides what appear to be disks and partitions to your OS.
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And the operating system is completely unaware that it's being "tricked."
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![Drive space][2]
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Opensource.com, [CC BY-SA 4.0][3]
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Because the LVM creates volume groups and logical volumes virtually, it makes it easy to resize or move them, or create new volumes, even while the system is running. Additionally, LVM provides features that are not present otherwise, like creating live snapshots of logical volumes, without unmounting the disk first.
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A volume group in an LVM is a named virtual container that groups together the underlying physical disks. It acts as a pool from which logical volumes of different sizes can be created. Logical volumes contain the actual file system and can span multiple disks, and don't need to be physically contiguous.
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### Features
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* Partition names normally have system designations like `/dev/sda1`. LVM volumes have normal human-understandable names, like `home` or `media`.
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* The total size of partitions is limited by the size of the underlying physical disk. In LVM, volumes can span multiple disks, and are only limited by the total size of all physical disks in the LVM.
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* Partitions can normally only be resized, moved, or deleted when the disk is not in use and is unmounted. LVM volumes can be manipulated while the system is running.
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* Partitions can only be expanded by allocating them free space adjacent to the partition. LVM volumes can take free space from anywhere.
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* Expanding a partition involves moving the data around to make free space, which is time-consuming and could lead to data loss during a power outage. LVM volumes can take free space from anywhere in the volume group, even on another disk.
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* Because it’s so easy to create volumes in an LVM, it encourages creating different volumes, like creating separate volumes to test features or to try different operating systems. With partitions, this process would be time-consuming and error-prone.
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* Snapshots can only be created in an LVM. It allows you to create a point-in-time image of the current logical volume, even while the system is running. This is great for backups.
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### Test setup
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As a demonstration, assume your system has the following drive configuration:
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```
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NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
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xvda 202:0 0 8G 0 disk
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`-xvda1 202:1 0 8G 0 part /
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xvdb 202:16 0 1G 0 disk
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xvdc 202:32 0 1G 0 disk
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xvdd 202:48 0 2G 0 disk
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xvde 202:64 0 5G 0 disk
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xvdf 202:80 0 8G 0 disk
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```
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#### Step 1. Initialize disks to use with LVM
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Run `pvcreate /dev/xvdb /dev/xvdc /dev/xvdd /dev/xvde /dev/xvdf`. The output should be:
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```
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Physical volume "/dev/xvdb" successfully created
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Physical volume "/dev/xvdc" successfully created
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Physical volume "/dev/xvdd" successfully created
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Physical volume "/dev/xvde" successfully created
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Physical volume "/dev/xvdf" successfully created
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```
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See the result using `pvs` or `pvdisplay`:
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```
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"/dev/xvde" is a new physical volume of "5.00 GiB"
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\--- NEW Physical volume ---
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PV Name /dev/xvde
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VG Name
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PV Size 5.00 GiB
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Allocatable NO
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PE Size 0
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Total PE 0
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Free PE 0
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Allocated PE 0
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PV UUID 728JtI-ffZD-h2dZ-JKnV-8IOf-YKdS-8srJtn
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"/dev/xvdb" is a new physical volume of "1.00 GiB"
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\--- NEW Physical volume ---
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PV Name /dev/xvdb
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VG Name
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PV Size 1.00 GiB
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Allocatable NO
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PE Size 0
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Total PE 0
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Free PE 0
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Allocated PE 0
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PV UUID zk1phS-7uXc-PjBP-5Pv9-dtAV-zKe6-8OCRkZ
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"/dev/xvdd" is a new physical volume of "2.00 GiB"
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\--- NEW Physical volume ---
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PV Name /dev/xvdd
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VG Name
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PV Size 2.00 GiB
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Allocatable NO
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PE Size 0
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Total PE 0
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Free PE 0
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Allocated PE 0
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PV UUID R0I139-Ipca-KFra-2IZX-o9xJ-IW49-T22fPc
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"/dev/xvdc" is a new physical volume of "1.00 GiB"
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\--- NEW Physical volume ---
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PV Name /dev/xvdc
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VG Name
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PV Size 1.00 GiB
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Allocatable NO
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PE Size 0
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Total PE 0
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Free PE 0
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Allocated PE 0
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PV UUID FDzcVS-sq22-2b13-cYRj-dXHf-QLjS-22Meae
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"/dev/xvdf" is a new physical volume of "8.00 GiB"
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\--- NEW Physical volume ---
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PV Name /dev/xvdf
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VG Name
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PV Size 8.00 GiB
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Allocatable NO
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PE Size 0
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Total PE 0
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Free PE 0
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Allocated PE 0
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PV UUID TRVSH9-Bo5D-JHHb-g0NX-8IoS-GG6T-YV4d0p
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```
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#### Step 2. Create the volume group
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Run `vgcreate myvg /dev/xvdb /dev/xvdc /dev/xvdd /dev/xvde /dev/xvdf`. See the results with `vgs` or `vgdisplay`:
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```
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\--- Volume group ---
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VG Name myvg
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System ID
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Format lvm2
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Metadata Areas 5
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Metadata Sequence No 1
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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 0
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Open LV 0
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Max PV 0
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Cur PV 5
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Act PV 5
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VG Size 16.98 GiB
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PE Size 4.00 MiB
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Total PE 4347
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Alloc PE / Size 0 / 0
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Free PE / Size 4347 / 16.98 GiB
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VG UUID ewrrWp-Tonj-LeFa-4Ogi-BIJJ-vztN-yrepkh
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```
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#### Step 3: Create logical volumes
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Run the following commands:
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```
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lvcreate myvg --name media --size 4G
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lvcreate myvg --name home --size 4G
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```
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Verify the results using `lvs` or `lvdisplay`:
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```
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\--- Logical volume ---
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LV Path /dev/myvg/media
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LV Name media
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VG Name myvg
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LV UUID LOBga3-pUNX-ZnxM-GliZ-mABH-xsdF-3VBXFT
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LV Write Access read/write
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LV Creation host, time ip-10-0-5-236, 2017-02-03 05:29:15 +0000
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LV Status available
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# open 0
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LV Size 4.00 GiB
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Current LE 1024
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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 252:0
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\--- Logical volume ---
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LV Path /dev/myvg/home
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LV Name home
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VG Name myvg
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LV UUID Hc06sl-vtss-DuS0-jfqj-oNce-qKf6-e5qHhK
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LV Write Access read/write
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LV Creation host, time ip-10-0-5-236, 2017-02-03 05:29:40 +0000
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LV Status available
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# open 0
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LV Size 4.00 GiB
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Current LE 1024
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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 252:1
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```
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#### Step 4: Create the file system
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Create the file system using:
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```
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mkfs.ext3 /dev/myvg/media
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mkfs.ext3 /dev/myvg/home
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```
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Mount it:
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```
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mount /dev/myvg/media /media
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mount /dev/myvg/home /home
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```
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See your full setup using `lsblk`:
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```
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NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
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xvda 202:0 0 8G 0 disk
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`-xvda1 202:1 0 8G 0 part /
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xvdb 202:16 0 1G 0 disk
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xvdc 202:32 0 1G 0 disk
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xvdd 202:48 0 2G 0 disk
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xvde 202:64 0 5G 0 disk
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`-myvg-media 252:0 0 4G 0 lvm /media
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xvdf 202:80 0 8G 0 disk
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`-myvg-home 252:1 0 4G 0 lvm /home
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```
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#### Step 5: Extending the LVM
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Add a new disk at `/dev/xvdg`. To extend the `home` volume, run the following commands:
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```
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pvcreate /dev/xvdg
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vgextend myvg /dev/xvdg
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lvextend -l 100%FREE /dev/myvg/home
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resize2fs /dev/myvg/home
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```
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Run `df -h` and you should see your new size reflected.
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And that's it!
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LVM enables extreme flexibility in how you configure your storage. Try it out, and have fun with LVM!
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* * *
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_This article was originally published on the [author's personal blog][4] and has been adapted with permission._
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/21/9/add-storage-lvm
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作者：[Ayush Sharma][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://opensource.com/users/ayushsharma
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/bus-storage.png?itok=95-zvHYl (Storage units side by side)
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[2]: https://opensource.com/sites/default/files/lvm.png (Drive space)
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[3]: https://creativecommons.org/licenses/by-sa/4.0/
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[4]: https://notes.ayushsharma.in/2017/02/working-with-logical-volume-manager-lvm
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