A Beginner's Guide To LVM - Page 5

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Submitted by falko (Contact Author) (Forums) on Sun, 2007-01-14 19:08. ::

5 Adding A Hard Drive And Removing Another One

We haven't used /dev/sdf until now. We will now create the partition /dev/sdf1 (25GB) and add that to our fileserver volume group.

fdisk /dev/sdf

server1:~# fdisk /dev/sdf
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won't be recoverable.


The number of cylinders for this disk is set to 10443.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

Command (m for help):
 <-- m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help):
 <-- n
Command action
   e   extended
   p   primary partition (1-4)

<-- p
Partition number (1-4): <-- 1
First cylinder (1-10443, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-10443, default 10443):
 <-- +25000M

Command (m for help): <-- t
Selected partition 1
Hex code (type L to list codes):
 <-- 8e
Changed system type of partition 1 to 8e (Linux LVM)

Command (m for help):
 <-- w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

Let's prepare /dev/sdf1 for LVM:

pvcreate /dev/sdf1

server1:~# pvcreate /dev/sdf1
  Physical volume "/dev/sdf1" successfully created

Add /dev/sdf1 to our fileserver volume group:

vgextend fileserver /dev/sdf1

Run

vgdisplay

VG Size should now be bigger than before:

server1:~# vgdisplay
  --- Volume group ---
  VG Name               fileserver
  System ID
  Format                lvm2
  Metadata Areas        5
  Metadata Sequence No  12
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                3
  Open LV               3
  Max PV                0
  Cur PV                5
  Act PV                5
  VG Size               116.43 GB
  PE Size               4.00 MB
  Total PE              29805
  Alloc PE / Size       11776 / 46.00 GB
  Free  PE / Size       18029 / 70.43 GB
  VG UUID               iWr1Vk-7h7J-hLRL-SHbx-3p87-Rq47-L1GyEO

That's it. /dev/sdf1 has been added to the fileserver volume group.

Now let's remove /dev/sdb1. Before we do this, we must copy all data on it to /dev/sdf1:

pvmove /dev/sdb1 /dev/sdf1

This can take some minutes:

server1:~# pvmove /dev/sdb1 /dev/sdf1
  /dev/sdb1: Moved: 1.9%
  /dev/sdb1: Moved: 3.8%
  /dev/sdb1: Moved: 5.8%
  /dev/sdb1: Moved: 7.8%
  /dev/sdb1: Moved: 9.7%
  /dev/sdb1: Moved: 11.6%
  /dev/sdb1: Moved: 13.6%
  /dev/sdb1: Moved: 15.6%
  /dev/sdb1: Moved: 17.5%
  /dev/sdb1: Moved: 19.4%
  /dev/sdb1: Moved: 21.4%
  [...]
  /dev/sdb1: Moved: 85.7%
  /dev/sdb1: Moved: 87.7%
  /dev/sdb1: Moved: 89.7%
  /dev/sdb1: Moved: 91.7%
  /dev/sdb1: Moved: 93.6%
  /dev/sdb1: Moved: 95.5%
  /dev/sdb1: Moved: 97.5%
  /dev/sdb1: Moved: 99.4%
  /dev/sdb1: Moved: 100.0%

Next we remove /dev/sdb1 from the fileserver volume group:

vgreduce fileserver /dev/sdb1

server1:~# vgreduce fileserver /dev/sdb1
  Removed "/dev/sdb1" from volume group "fileserver"

vgdisplay

server1:~# vgdisplay
  --- Volume group ---
  VG Name               fileserver
  System ID
  Format                lvm2
  Metadata Areas        4
  Metadata Sequence No  16
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                3
  Open LV               3
  Max PV                0
  Cur PV                4
  Act PV                4
  VG Size               93.14 GB
  PE Size               4.00 MB
  Total PE              23844
  Alloc PE / Size       11776 / 46.00 GB
  Free  PE / Size       12068 / 47.14 GB
  VG UUID               iWr1Vk-7h7J-hLRL-SHbx-3p87-Rq47-L1GyEO

Then we run

pvremove /dev/sdb1

/dev/sdb1 shouldn't be listed as a physical volume anymore:

pvdisplay

server1:~# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sdc1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               1682
  Allocated PE          4279
  PV UUID               40GJyh-IbsI-pzhn-TDRq-PQ3l-3ut0-AVSE4B

  --- Physical volume ---
  PV Name               /dev/sdd1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               4681
  Allocated PE          1280
  PV UUID               4mU63D-4s26-uL00-r0pO-Q0hP-mvQR-2YJN5B

  --- Physical volume ---
  PV Name               /dev/sde1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               5705
  Allocated PE          256
  PV UUID               3upcZc-4eS2-h4r4-iBKK-gZJv-AYt3-EKdRK6

  --- Physical volume ---
  PV Name               /dev/sdf1
  VG Name               fileserver
  PV Size               23.29 GB / not usable 0
  Allocatable           yes (but full)
  PE Size (KByte)       4096
  Total PE              5961
  Free PE               0
  Allocated PE          5961
  PV UUID               1xgo2I-SBjj-0MAz-lmDu-OLZ1-3NdO-mLkS20

You could now remove /dev/sdb from the system (if this was a real system and not a virtual machine).


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