-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of Scott Silva Sent: Tuesday, April 03, 2007 12:59 PM To: centos@centos.org Subject: [CentOS] Re: Where is the LVM config stored?
WipeOut spake the following on 4/3/2007 8:23 AM:
Ross S. W. Walker wrote:
-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of WipeOut Sent: Tuesday, April 03, 2007 6:40 AM To: CentOS mailing list Subject: [CentOS] Where is the LVM config stored?
Hi,
I am trying to migrate one of my systems to a VMware virtual machine.. The PC is an IDE drive using LVM and the
virtual machine is
a SCSI drive using ordinary partitions..
Basically I rsynced the entire filesystem from the physical to the virtual machine and that seemed to work just fine.. I
installed grub
onto the drive in the virtual machine and its booting fine..
What tool did you use to copy the host filesystem?
To what physical medium did you copy it to, vmware virtual
disk file
or physical partition/logical volume?
The problem comes when the new system trys to scan for
the LVM setup
that was on the previous PC.. I thought it would scan the
drive, and
seen that there are no LVM partitions and move on but it
doesn't it
has a kernel panic and flashes the cap lock and scroll
lock LED's on
the keyboard.. Obviously somewhere its being told there
should be an
LVM partition or its being told to scan hda rather than sda..
The LVM information is stored in the disk volume itself, there are backup copies of the configuration routinely dumped to /etc/lvm/backup, and archive copies of volume groups stored in /etc/lvm/archive.
Make sure this "copy" of your physical host's drive isn't somehow being accessed by the physical host at the same time as the virtual host.
I have checked the grub.conf and fstab files and they are
all right
for the new drive setup..
So where is the LVM config? How do I tell it there are now LVM volumes that need to be accessed?
If the PV headers were copied in the volume copy it should pick those up on the pvscan, then vgscan will see any volume groups defined within the PVs and lvscan should find any LVs within the volume groups.
-Ross
Maybe I should explain exactly what I did because perhaps I
am doing it
all wrong and thats why I am having so many issues..
I have a Physical Centos box (we will call it PC) and I
want to turn it
into a Virtual Centos box (VC).. I created the virtual
machine in the
VMWare server console and then installed VC with a minimum Centos4 install.. I then went to PC and ran rsync with the various
switches to
copy the entire filesystem from PC to VC across the
network.. I excluded
/dev, /proc and /sys.. I also used the --delete option to remove any files that exited on VC that were no longer on PC.. Then before rebooting VC I checked fstab and grub.conf files to make
sure they were
correct.. Finally I restarted VC and booted from CD1 in
rescue mode to
run grub-install to get the boot sector and start up
working right..Then
rebooted VC.. It starts up and then freaks when trying to
sort out the
LVM volumes..
The difference between PC and VC is that in VC I have
decided to use a
scsi drive (apparently better performance) and in PC its an
IDE and I
have made the virtual drive bigger.. I have tried running
PC with and
without LVM (in other words using normal formatted
partitions) and it
seems to have the same problem.. So even when no LVM
volumes exist its
still looking for them..
Obviously I have both systems live an running when I am
doing the data
transfer.. There are no errors but would this cause a major issue?
How do you migrate form physical to virtual?
Thanks..
Going from an IDE drive to a SCSI drive means you will have to make an initial ramdisk on the new system (initrd). The scsi drivers are modules in the kernel, and without an initrd with the drivers included and enabled, you can't mount the root to finish booting. Look here for a fix; http://kbase.redhat.com/faq/FAQ_80_3902.shtm
Yes, of course, and if your rsync'd modprobe.conf didn't include the SCSI driver it wouldn't make it into the initrd unless you modified modprobe.conf and manually added it afterward before running mkinitrd.
I don't see how an emulated scsi drive will perform any better than an emulated IDE drive, but I suppose it is possible.
I guess it would depend if it emulated tagged queuing and command recursion and if it implemented it decently, but conceivably it is possible to have emulated scsi that out performs emulated ide with these two features implemented.
-Ross
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