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Old 01-28-2010, 12:44 AM   #1
fizeelinux
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Registered: Nov 2008
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LVM Basics


Hi all,

I am trying to learn LVM concepts and created Physical and Volume group and output are as follows.

Quote:
[root@srv-ftp /]# /sbin/fdisk /dev/sdb

The number of cylinders for this disk is set to 30401.
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)

Command (m for help): p

Disk /dev/sdb: 250.0 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 1 12159 97667136 8e Linux LVM
/dev/sdb2 12160 18239 48837600 8e Linux LVM
Can anyone please help me in explaining this output? I can understand that it is a 250GB harddisk and it has two partions of LVM type.How can i see the unpartitioned size so that i can extend or create a new partition.How is the cylinder size related to the harddisk.What does 30401 and 16065 * 512 mean ?Awaiting for your reply.Thanks in advance.

Last edited by fizeelinux; 01-28-2010 at 12:45 AM.
 
Old 01-28-2010, 12:59 AM   #2
ongte
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Location: Penang, Malaysia
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Disk /dev/sdb: 250.0 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 1 12159 97667136 8e Linux LVM
/dev/sdb2 12160 18239 48837600 8e Linux LVM

In Red is your Total # of Cylinders.
In Blue is the last Cylinder of your 2nd partition. That means you still have space between 18240 & 30401 = 12161 Cylinders.

Take 12161 and times the Unit 8225280 bytes will give you your remaining space of 100,027,630,080 bytes. About 93GB. All this is basic partition concepts and does not really have anything to do with LVM.

The partitions marked as Linux LVM are used as the physical volumes. From them you can create volume groups and logical volumes.
To view LVM details use:
pvdisplay
vgdisplay
lvdisplay

Not in front of a *nix box, so can't tell you the exact commands. But basically, what you need to do is create another partition of type Linux LVM in the free space available.
Then use pvcreate to mark the partition as a physical volume(PV).
Use vgextend to add this PV into your current volume group (VG)
and lvextend to extend your logical volume (LV)
Finally use resize2fs to resize the filesystem into the new partition size.

Last edited by ongte; 01-28-2010 at 01:06 AM.
 
Old 01-28-2010, 01:03 AM   #3
EricTRA
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Registered: May 2009
Location: Gibraltar, Gibraltar
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Hello,

Have a look at this LVM Tutorial, it's very easy to follow and understand and explains the commands with nice examples.

Kind regards,

Eric
 
Old 01-29-2010, 02:24 AM   #4
fizeelinux
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Registered: Nov 2008
Posts: 91

Original Poster
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Quote:
Originally Posted by ongte View Post
Disk /dev/sdb: 250.0 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 1 12159 97667136 8e Linux LVM
/dev/sdb2 12160 18239 48837600 8e Linux LVM

In Red is your Total # of Cylinders.
In Blue is the last Cylinder of your 2nd partition. That means you still have space between 18240 & 30401 = 12161 Cylinders.

Take 12161 and times the Unit 8225280 bytes will give you your remaining space of 100,027,630,080 bytes. About 93GB. All this is basic partition concepts and does not really have anything to do with LVM.

The partitions marked as Linux LVM are used as the physical volumes. From them you can create volume groups and logical volumes.
To view LVM details use:
pvdisplay
vgdisplay
lvdisplay

Not in front of a *nix box, so can't tell you the exact commands. But basically, what you need to do is create another partition of type Linux LVM in the free space available.
Then use pvcreate to mark the partition as a physical volume(PV).
Use vgextend to add this PV into your current volume group (VG)
and lvextend to extend your logical volume (LV)
Finally use resize2fs to resize the filesystem into the new partition size.
Thanks a lot.I really appreciate that.Thanks for the info.
 
  


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