Trying to understand LVM

[rtcary]

It appears that upon installing the new Fedora 3, I got dumped head first into Logical Volume Manager (LVM), the way Red Hat is managing file systems. After snooping around this and other forums and using Google, I have increased my understanding somewhat about Fedora 3 and it's file system management, yet in no way am I confortable with understanding what is really going on. Here is what I have found out so far:

* The file system is managed by lvm2 (Logical Volume Manager) which creates LVM entries.

* #mount displays

# This file is edited by fstab-sync - see 'man fstab-sync' for details
/dev/VolGroup00/LogVol00 / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /dev/shm tmpfs defaults 0 0
none /proc proc defaults 0 0
none /sys sysfs defaults 0 0
/dev/VolGroup00/LogVol01 swap swap defaults 0 0
/dev/hdc /media/cdrom auto pamconsole,exec,noauto,managed 0 0
/dev/fd0 /media/floppy auto pamconsole,exec,noauto,managed 0 0

* #fdisk -l displays

Disk /dev/hda: 81.9 GB, 81964302336 bytes
255 heads, 63 sectors/track, 9964 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/hda1 * 1 13 104391 83 Linux
/dev/hda2 14 9964 79931407+ 8e Linux LVM

Disk /dev/hdb: 40.0 GB, 40020664320 bytes
255 heads, 63 sectors/track, 4865 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/hdb1 * 1 4865 39078081 8e Linux LVM


* #lvdisplay displays

--- Logical volume ---
LV Name /dev/VolGroup00/LogVol00
VG Name VolGroup00
LV UUID obhKwl-oiML-P38I-2x64-jtdW-o0El-B8jMsW
LV Write Access read/write
LV Status available
# open 1
LV Size 112.91 GB
Current LE 3613
Segments 2
Allocation inherit
Read ahead sectors 0
Block device 253:0

--- Logical volume ---
LV Name /dev/VolGroup00/LogVol01
VG Name VolGroup00
LV UUID 0VrTdl-DQIm-5qlp-gBCE-4Y4w-L9uQ-FmRS8G
LV Write Access read/write
LV Status available
# open 1
LV Size 512.00 MB
Current LE 16
Segments 1
Allocation inherit
Read ahead sectors 0
Block device 253:1

It appears that the LV size of 112.91 GB is the combined size of the two HD's. In other words, the LVM system has combined the hard drives into one logical entry. Could this be?

Does anyone on this forum have a good understanding of the LVM system in Fedora 3?

Todd

[markkuk]

Yes, the installer combines all available hard disk space (except the /boot partition) into a LVM volume group.

[w5set]

Black magic--deep secrets but most will be revealed here...
http://www.tldp.org/HOWTO/LVM-HOWTO/index.html

[catscit]

Originally Posted by rtcary

# This file is edited by fstab-sync - see 'man fstab-sync' for details
/dev/VolGroup00/LogVol00 / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /dev/shm tmpfs defaults 0 0
none /proc proc defaults 0 0
none /sys sysfs defaults 0 0
/dev/VolGroup00/LogVol01 swap swap defaults 0 0
/dev/hdc /media/cdrom auto pamconsole,exec,noauto,managed 0 0
/dev/fd0 /media/floppy auto pamconsole,exec,noauto,managed 0 0

How can I add a disk not using lvm but using the conventional way of fdisking it and adding it to fstab? I don't want 1 giant partition, I want seperate disks I can put in other linux boxes and read!

Looking at the first line of fstab I get the impression that "just" adding a line to fstab is not such a good idea.

[markkuk]

Originally Posted by catscit

How can I add a disk not using lvm but using the conventional way of fdisking it and adding it to fstab?

You do that by conventionally fdisking it and adding it to fstab
There's no problem in mixing LVM logical volumes and ordinary partitions in a system.

[catscit]

Originally Posted by markkuk

You do that by conventionally fdisking it and adding it to fstab
There's no problem in mixing LVM logical volumes and ordinary partitions in a system.

Won't fstab-sync overwite my fstab entries?
Or does this only happen when I change something to the lvm setup?

Sorry for being such a pain in the ****. I'm replacing my suse mail server, suse file server and freesco firewall with 1 fedora box (i really like fedora!) and i like to find out how these things work before I move over all my data to the fedora box and find out it's inaccesable because i made the wrong assumption... (i do make regular backups though...)

thanx

[markkuk]

The entries handled by fstab-sync are marked by the "managed" option. As you see, only removable media (floppy, CD-ROM) are marked managed and all hard disk file systems (both LVM and ordinary) aren't managed by fstab-sync.

[catscit]

Added the line to fstab and it works flawlessly.
Thanx for the support guys!