mirrored logical volume configuration in Red Hat Enterprise Linux

Posted: April 22, 2015 in RAID and LVM
Tags: , , , ,

In the world of computer  data is more important and with increase in internet users it’s increasing very fast and hence now storing data is most challenging task.Now it is not good to store your data on single drive when you know your data is important,because in case of disk failure your data will loss and it will be a huge disaster.So in place of storing data on a single disk it will be intelligent decesion to store your data on multiple disk such that if one disk fails your data is still safe on second disk.

There are two technology or you can say there are two methods commonly used to store data on multiple disk:

(1)One is to strore data on multiple disk through RAID and

(2)other is through LVM.

Since LVM provides us more flexblity  in handling disk and managing data,so most of us prefer configuring LVM.

In This article i have mentioned how to create and configure mirrored logical volume.here we learn the fundamental concept of LVM Mirroring and also learn to create,manage ad maintain LVM mirror in Linux in few simple steps.

While writing this article i assume that you already know how to create partition in linux.But if you don’t know or you a new user you can read our below article.

Read:HOW TO CREATE PARTITION IN LINUX.

Read:HOW TO CREATE STRIPED LOGICAL VOLUME IN LINUX

lvm mirroring

 

MIRRORED LOGICAL VOLUME:

Before learning how to create or configure mirrored LVM just have few words about mirrored LVM.When we are using the word mirror it means it maintains identical copies of data on different devices.So in Mirrored Logical Volume when data is written to one device,it is written to a second device as well and hence mirroring the data,which provides protection in case of device failure.

So you will be excited to know what will happen if one leg of mirror fails?

Answer is if one leg of mirror fails the logical volume becomes a Linear Volume and we can still access data.

Note:In above diagram you can see a LOG sector which is used by LVMto keep track of which regions are in syc with the mirror or mirrors.

STEP 1:After creating partitions create Physical Volumes using pvcreate.

[root@localhost ~]# pvcreate /dev/sda{5,6,7,8}

Now see physical volume attributes using pvs command.

[root@localhost ~]# pvs
PV         VG   Fmt  Attr PSize   PFree
/dev/sda5       lvm2 a-   196.76m 196.76m
/dev/sda6       lvm2 a-   203.92m 203.92m
/dev/sda7       lvm2 a-   407.87m 407.87m
/dev/sda8       lvm2 a-   203.92m 203.92m

 

STEP 2:Now create Volume Group named “mirror_vg00” using above physical volumes.

[root@localhost ~]# vgcreate mirror_vg /dev/sda{5,6,7,8}
Volume group “mirror_vg” successfully created

 

Display volume group attributes.
[root@localhost ~]# vgs
VG        #PV #LV #SN Attr   VSize   VFree
mirror_vg   4   0   0 wz–n- 996.00m 996.00m

 

STEP 3:Now Create a Mirrored LVM.
[root@localhost ~]# lvcreate -L 200M -m1 -n mirror_lv mirror_vg
Logical volume “mirror_lv” created

Display mirrored LVM attributes:
[root@localhost ~]# lvs -a -o +devices
LV                   VG        Attr   LSize   Origin Snap%  Move Log            Copy%  Convert Devices
mirror_lv            mirror_vg mwi-a- 200.00m                    mirror_lv_mlog 100.00         mirror_lv_mimage_0(0),mirror_lv_mimage_1(0)
[mirror_lv_mimage_0] mirror_vg iwi-ao 200.00m                                                  /dev/sda6(0)
[mirror_lv_mimage_1] mirror_vg iwi-ao 200.00m                                                  /dev/sda7(0)
[mirror_lv_mlog]     mirror_vg lwi-ao   4.00m                                                  /dev/sda5(0)

 

STEP 4: Create File system and mount and confirm mounting of  Mirrored LVM.

[root@localhost ~]# mkdir /mirror

[root@localhost ~]# mkfs.ext4 /dev/mirror_vg/mirror_lv

[root@localhost ~]# mount /dev/mirror_vg/mirror_lv  /mirror/

 

[root@localhost ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1             9.7G  2.8G  6.4G  31% /
tmpfs                 504M  524K  504M   1% /dev/shm
/dev/mapper/mirror_vg-mirror_lv
194M  5.6M  179M   4% /mirror

 

 

Now Learn how to Delete or Destroy Mirrored LVM.

Step1:Unmount LVM

[root@localhost ~]# umount /mirror/

Step2:Check and confirm your Unmount
[root@localhost ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1             9.7G  2.8G  6.4G  31% /
tmpfs                 504M  524K  504M   1% /dev/shm

Step3:Remove mirrored lvm.
[root@localhost ~]# lvremove /dev/mirror_vg/mirror_lv
Do you really want to remove active logical volume mirror_lv? [y/n]: y
Logical volume “mirror_lv” successfully removed

Step5:Confirm removal of LVM using lvs
[root@localhost ~]# lvs

Step6:Remove volume group and confirm its removal.
[root@localhost ~]# vgremove /dev/mirror_vg
Volume group “mirror_vg” successfully removed
[root@localhost ~]# vgs
No volume groups found

Step7:Check physical volume,if exist them remove it using pvremove and then confirm its removal.
[root@localhost ~]# pvs
PV         VG   Fmt  Attr PSize   PFree
/dev/sda5       lvm2 a-   196.76m 196.76m
/dev/sda6       lvm2 a-   203.92m 203.92m
/dev/sda7       lvm2 a-   407.87m 407.87m
/dev/sda8       lvm2 a-   203.92m 203.92m
[root@localhost ~]# pvremove /dev/sda{5,6,7,8}
Labels on physical volume “/dev/sda5” successfully wiped
Labels on physical volume “/dev/sda6” successfully wiped
Labels on physical volume “/dev/sda7” successfully wiped
Labels on physical volume “/dev/sda8” successfully wiped

If you like it share it!

If you have any doubts feel free to ask through comment section.

If you have any suggestion,You welcome! just mention your valuable  suggestion through comments.

Leave a Reply

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s