Linux LVM (Logical Volume Manager) for CentOS on Azure?

Hi. I am trying out Azure and installed a OpenLogic CentOS 6 virtual machine. I note that it is not running LVM (Logical Volume Manager) by default. I would like to ask if it is possible to:
1. have CentOS Linux installed with LVM by default when creating a Linux virtual machine on Azure
2. switch to LVM after adding a new disk
On the other hand, is it a good idea to use LVM at all? Will it affect performance, features on Azure?
Thanks.

Hi,
Based on my experience, you can add disk to an Azure VM. You can install the Logical Volume Manager to manage the disks attached to the VM. In addition, there is no Linux VM with LVM installed by default. If you want to have this, please submit your requirement
in Azure feedback:
http://feedback.azure.com/forums/34192--general-feedback
In addition, since you can have only one OS system disk for an Azure VM, this limitation may make multi-disk logical volume manager setups unworkable.
Best regards,
Susie
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Hi I've been looking into backing up one of my LVM logical volumes and I came across this (http://www.novell.com/coolsolutions/appnote/19386.html) article.
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You can use 2 partitions on the same disk to create a RAID array, but that defeats the whole purpose of RAID.
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Extending LVM logical volume

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Segments 2
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Logical Volume Manager

I am planning on installing Arch on a laptop soon. I have played with it in VirtualBox on a separate computer, and I am going to hope that it works with my touchpad / wireless mouse.
I might butcher some jargon in this, but this is how I think LVMs work, and I would like to make sure.
I am going to make partitions for boot, swap, /, and /home.
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I only have 1 HD, and I'm mostly doing this because while I do have room to have too much space on /, if I end up only using around 4GB, I would like to have that 11GB on my /home for music or videos.
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After that, this is where I am confused.
The Arch Wiki says:
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This will create a logical volume that you can access later with /dev/mapper/Volgroup00-lvolhome or /dev/VolGroup00/lvolhome. Same as with the volume groups you can use any name you want for your logical volume when creating it.
So later, I would turn this into my home partition during the Arch installation? I would create a lvolswap, and a lvolroot?
Then, during the installation process, I would format them to ext3, and mount them as /home, /, and then select lvolswap as my swap partition?
That's about it for now, I guess.
Last edited by COMMUNISTCHINA (2008-08-15 21:53:41)

COMMUNISTCHINA wrote:
Berticus wrote:
COMMUNISTCHINA wrote:I dunno. I tried using LVM on a virtualbox and I keep getting a kernel panic. I followed the Wiki.
If I put GRUB on /boot, it doesn't work, but I got it to work if I installed it on the / LV.
odd, to my knowledge grub can't be on an LVM. why not install grub on MBR?
I actually figured this out maybe an hour ago.
I changed my GRUB configuration file, but since it's in a virtualbox, out of habit I type arch root=/dev/sda3 on startup, but I needed to type root=/dev/VG00/lvolroot. I had grub on /boot (not on the LVM), but when I was trying to boot, I told it to go to the wrong place for root. I could probably unmount the .iso for the vbox, but whatever.
I will read a little more about RAID.
If I end up figuring out how to do it, would I need my external hooked up to it all the time? I have tote the laptop around, and I wouldn't want the external mucking up the portability.
I wasn't aware you were on a laptop. In that case, a file server would do you best. But cheapest solution would be just to stick with an external hard drive and not RAID.

Extending an LVM Logical Volume to Another Disk

I have read the article in the wiki and also this guide since my drives are encrypted. I have already set up arch on one drive with LVM on top of an encrypted volume (following the linked guide strictly with exceptions on the cipher and the partitioning). So far everything works very well but I'm only halfway where I want to end up. Additional to the one HDD I want to use two more, all of them encrypted (no problem here) and one logical volume spread across all three drives (problem be here).
So, to clarify, on /dev/sda I have two partitions, /boot (unencrypted, 130 MB) and /dev/sda2 (encrypted, ~2TB) on which the LVM volumes are.
/dev/sda2 is added to vgroup and has several logical volumes of which /home is the largest.
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3) From what I have read so far I could extend /home now with lvextend -l +100%FREE vgroup/home, is that correct? After that I would only have to extend the file system (ext4) on /home and it would be done?
I hope it is clear what I am trying to do, if not please do ask. Thanks in advance for reading all of this.

Turns out this is not quite over yet. After successfully dealing with LVM I was about to reboot when something occurred to me: The second HDD (sdc1) will not be decrypted at boot and I have no idea what would happen if LVM tries to mount a volume that is spread across two disks of which one is not available.
So I searched for some time and everything I could find was this thread. Well, he is talking about altering the encrypt hook and generate a new initramfs to be able to enter more than one cryptdevice in grub. I have never dealt with hooks before and never got my hands on bash script like this. Now my options are pretty weak: I could do what he describes although I have no idea how it works or I could revert all the changes to LVM. Naturally I chose option number one, parsed the hook, edited the menu.lst, rebooted and "Waiting 10 seconds for device /dev/sda2".
So yeah it's my fault for trying something I have no clue about.
I tried to access the volumes from the live cd, but even though I decrypted the drives and loaded up lvm with vgchange -a -y I can not access the logical volumes. I naively tried to access the files such as menu.lst but I can't get there. Probably because I just lack the knowledge how to do that. But even if I would be able to access the files, could I build the hooks of my system from within the live cd?
Last edited by venehan_snakes (2011-10-18 16:49:48)

Veritas volume manager for solaris 10

Hi All
which version veritas volume manager will support solaris 10 06/06.
can you just update a link for reference
Regards
RPS

Hello,
we are currently using solaris 9 with veritas volume manager 3.5.So i would like to know if i upgrade to solaris 10 06/06.whether i can use 3.5 or not.
Using the Veritas (Symantec) support site, I have found the following document
VERITAS Storage Solutions 3.5 Maintenance Pack 4 for Solaris
http://seer.support.veritas.com/docs/278582.htm
The latest supported version listed for VxVM 3.5 with MP4 applied is Solaris 9. That means the answer is NO.
I understand that searching the Veritas knowledge base might be tough and time consuming, but it's their product ...
Michael

[solved] Filesystem check fail - Cannot access LVM Logical Volumes

I am getting a "File System Check Failed"on startup, I recently did a full system upgrade but I'm not entirely sure that the cause of the issue as I don't reboot very often.
I get the error right before this line is echo'ed out:
/dev/mapper/Arch_LVM-Root:
The super block could not be read or does not describe a correct ext2 filesystem...
this is odd because the only ext2 filesystem I have is on an non-LVM boot partition...
I can log-in and mount / as read/write and I can activate LVM with
modprobe dm-mod
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vgchange -ay Arch_LVM
and they show up in lvdisplay but their status is "NOT available"
I just need to mount these logical volumes so I can retrieve some personal data in my home directory, I am also hesitant to use LVM again if I can't retrieve my data.
any suggestions?
Last edited by action_owl (2010-08-15 02:15:58)

I just popped in the install disk and was able to mount and access the LVM groups as expected, something must have been wonky with my filesystem

[solved]Booting a LVM logical volume spanned across two LUKS paritions

I have two partitions formatted as LUKS that both physical LVM volumes for a logical LVM partition that holds my root filesystem. I can't seem to figure out what the kernel line should be. I tried specifying cryptdevice twice, but it seems to only want to take one of the cryptdevice= options. What now?
Last edited by synthead (2011-12-09 16:17:06)

I found this: https://bbs.archlinux.org/viewtopic.php … 95#p827495
Modifying /lib/initcpio/hooks/encrypt with the patch as recommended did the trick. I'll file a feature request for this

Rvm - Ramdisk volume manager for Arch

Hi,
I tried an experiment, this is a little tool that allows you to create tmpfs based ramdisks with Arch Linux installed on them. This script depends on `arch-install-scripts' as it uses pacstrap.
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sudo ./rvm create arch /home/bla/arch-mnt
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Code is available on github
Last edited by dimigon (2012-09-20 14:35:28)

Hi,
I tried an experiment, this is a little tool that allows you to create tmpfs based ramdisks with Arch Linux installed on them. This script depends on `arch-install-scripts' as it uses pacstrap.
You can for example do:
sudo ./rvm create arch /home/bla/arch-mnt
This will essentially install arch in `/home/bla/arch-mnt' (base and base-devel so far). The target dir `arch-mnt' will automatically be mounted as tmpfs (2G at the moment, although a command line option for the preferred size would be useful). On top of this a .tgz of the installation will be created and placed in RVM_VOLUMES_PATH (which needs to be set manually in the shell script for now, typically `/home/<user>/.rvm').
We can then do:
sudo ./rvm start arch /home/bla/arch-mnt
This will unpack the `arch.tgz' from RVM_VOLUMES_PATH into the mount point. We can then use `arch-chroot'.
Similarly to stop the ramdisk we do:
sudo ./rvm stop arch /home/bla/arch-mnt
This will backup everything from the mount point to a .tgz and copy it back to RVM_VOLUMES_PATH.
There are a couple of things that could be done better and will be, this is just a barebones version of the script. We could for example have rc.d/systemd scripts to start/stop etc.
Code is available on github
Last edited by dimigon (2012-09-20 14:35:28)

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more info here: https://bbs.archlinux.org/viewtopic.php?pid=1209271
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volumeicon, create an icon in tray, if you leftclick it you can enable/disable volume, if you rightclick it open a terminal with alsamixer.
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10g ASM on Logical Volumes vs. Raw devices and SAN Virtualization

We are looking at setting up our standards for Oracle 10g non-rac systems. We are looking at the value of Oracle ASM in our environment.
As per the official Oracle documentation, raw devices are preferred to using Logical Volumes when using ASM.
From here: http://download.oracle.com/docs/cd/B19306_01/server.102/b15658/appa_aix.htm#sthr
ef723
"Note: Do not add logical volumes to Automatic Storage Management disk groups. Automatic Storage Management works best when you add raw disk devices to disk groups. If you are using Automatic Storage Management, then do not use LVM for striping. Automatic Storage Management implements striping and mirroring."
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"10) Avoid using a Logical Volume Manager (LVM) because an LVM would be redundant."
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Additionally, we are using a an IBM DS8300 SAN with IBM SAN Volume Controller (SVC) in front of it. Hence, we already have storage virtualization and I/O balancing at the SAN/hardware level.
I'm looking for a little clarification to the following questions, as my understanding of their responses seem to confict:
QUESTION #1: Can anyone clarify/provide additional detail as to why Logical volumes are not preferred when using Oracle ASM? Does the argument still hold in a SAN Virtualized environment?
QUESTION #2: Does virtualization at the software level (ASM) make sense in our environment? As we already have I/O balancing provided at the hardware level via our SVC, what do we gain by adding yet another level of I/O balancing at the ASM level? Or as in the
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Basically, in an intelligent storage environment (i.e. SVC), you're not getting a 100% bang for the buck by using ASM. Which is the cat's meow in a commodity hardware/unintelligent storage environment.
Using ASM in a SVC environment potentially wastes CPU cycles having ASM balance i/o that is already balanced on the backend (sure if you shuffle a deck of cards that are already shuffled you're not doing any harm, but if they're already shuffled - then why are you shuffling them again??).
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Your vote may be different....just make sure you're putting in a solution to a problem and not a solution that's looking for a problem(s).
And there's the whole culture of IT thing as well (i.e. do your storage guys know what you're doing and vice versa).....which can destroy any technological solution, regardless of how great it is.

Linux LVM (Logical Volume Manager) for CentOS on Azure?

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