RHCE Learning Notes-LVM logical volumes

This section learns how to create snapshots of LVM,LVM and related configurations for raid.

For ordinary partitions, the scale is not high, once the partition format is complete, it is difficult to flexibly increase or reduce the size of the partition. To solve this problem, you can use LVM (logical volumes). The basic process is to initialize the physical disk or partition as a physical volume (PV), then add PV to the VG (volume group), and finally divide the logical partition (LVM) on the VG, which can be formatted and mounted as normal partitions.

First Look at PV

A new disk is divided into 6 partitions by gdisk, each partition 2G, is set to LVM type

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Create PV

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After you create the PV, you need to create the VG and then add the PV to the VG

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You can view the specific information through the Vgdisplay, note that the size of the PE is 4M, this is the smallest calculation unit of increase or decrease

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Enter VG, tab two times to view related commands

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We can continue to add new partitions to the VG.

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I did not convert the Sdc7 into PV, but added directly to the VG, but once added he automatically initialized to PV.

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Can add natural can reduce

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The VG is ready to create the LVM.

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The LV related commands are as follows, can be added, reduced, displayed, converted, etc.

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Create a 110M-sized logical volume

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Confirm

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Note that his size is actually 112M, because the size of the PE is 4M, this 4M is the smallest unit, can not break open, so 28 PE is 112M

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112 divided by 4, just 28.

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Large L can specify the size directly, small l is the value of the specified number of PE

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You can also set a percentage of the remaining space

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Delete a logical volume

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For logical volumes that have been created, they can be formatted and mounted as normal partitions

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To extend a logical volume 200M, note that his file system is still 109M unchanged, and we also need to populate the file system with whitespace. This is similar to the Windows virtual machine inside the expansion of the hard disk, the same need to use the DiskPart extend command to extend the file system.

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Rhel can be used XFS_GROWFS to expand the Xfs file system, or directly with the RESIZE2FS to deal with the device

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Note that the XFS system only grows and cannot be reduced! So if you need to reduce LVM, partitions can only use EXT4.

Here's a demonstration of how to expand or shrink ext4 LVM

First, create a 100M Lv2

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Mount to/bb

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Expansion of LVM:

100M expansion

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Populating the file system

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To reduce LVM:

Then Umount, check the Lv2 file system for errors, and then first need to reduce the file system size, here to 120M

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Then reduce the size of the LVM and reduce the 70M

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In addition to being able to increase and decrease LVM, you can also take snapshots. Many of the principles of backup software, such as the virtual machine is to take a snapshot of the disk, and then to the snapshot backup, if the time of the backup to write new information, the information is saved in a new snapshot, the backup is finished before the changes are written back to disk; If the snapshot space is not enough, you can imagine the consequences are catastrophic Beans have met many similar problems on Veeam B&r and ESXi.

Create a snapshot, specify a space of 100M, you can view the snapshot information

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Create a mount point, mount the snapshot, BB inside is attached to my original lvm,cc inside is a snapshot, you can find their content is the same

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Write a file in BB and CC to see, no problem

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The contents of the snapshot can be re-written back to the original LVM via Lvconvert

For example

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After the restart found/bb inside the manually created files are not, but the contents of the snapshot are written in

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Finally see how soft RAID is configured. RAID fundamentals are not covered, this is it common sense. Windows can set up soft Raid,rhel with similar functionality from the Win2000 start. Personally feel that soft raid is no use, after all, the motherboard almost all support the installation of hard raid, production environment and no one will do a server to do a soft raid, these are configured on the host hard disk or SAN.

Simply look at the creation and deletion of soft raid, the command used is Mdadm

Created a RAID5,

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View Details

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Can be formatted and mounted

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Remove Uninstall raid

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This article is from the "Mapo Tofu" blog, please be sure to keep this source http://beanxyz.blog.51cto.com/5570417/1603883

RHCE Learning Notes-LVM logical volumes