Re: [Openstack] Cinder's LVM vg creation when installing Grizzly

Tue, 14 May 2013 08:31:26 -0700

Hi, 
please see my answers below

Razique Mahroua - Nuage & Co
Tel : +33 9 72 37 94 15


Le 14 mai 2013 à 17:06, "Chris Bartels" <ch...@christopherbartels.com> a écrit :

Hi,
 
I have questions regarding this part of the Grizzly install guide that’s up on github:
 

·         Finally, don't forget to create a volumegroup and name it cinder-volumes:

·         dd if=/dev/zero of=cinder-volumes bs=1 count=0 seek=2G
dd is a binary that allows you to copy a file - in that case from the special device to the file called "cinder-volumes" (it's cinder-volume without s actually by default)

·         losetup /dev/loop2 cinder-volumes
You mount that file as a loop file so cinder (Linux before that actually) will see it as a devie

·         fdisk /dev/loop2
You format that file-device

·         #Type in the followings:
·         n
You create a new partition

·         p
You declare is as a primary partition

·         1
It' the first one

·         ENTER
You validate the first sector

·         ENTER
Then the last one

·         t
Then you change the partition type

·         8e
8e is the LVM code

·         w
You write the changes then exit :)

·         Proceed to create the physical volume then the volume group:

·         pvcreate /dev/loop2
You declare a new physical LVM volume 

·         vgcreate cinder-volumes /dev/loop2
You create a new volume group on the physical volume you previously created

Note: Beware that this volume group gets lost after a system reboot. (Click Here to know how to load it after a reboot)

Yes because the loop device gets removed, you can add an entry inside fstab that would mount the loop file

 
First, I don’t know what all those commands are doing, in particular with the dd stuff, and I’m reluctant to be doing stuff with that which I don’t understand, so if someone could explain what that’s all about I’d appreciate it. If that’s how it _must_ be done, I’d like to know.
 
Secondly, I’m wondering if I could make life easier and not have to bother with the extra stuff regarding making the vg come back after reboot, which the instructions link to how to do, if I were to simply do the cinder vg with the installer & install Ubuntu with 100GB (out of 1000GB) of the disk made available to the guided LVM partitioning during the initial install, and use the rest as a cinder-volumes vgcreate’d group that gets mounted normally at each boot like everything else does.
If you have a disk dedicated for Cinder (or a cluster, whatever) you can use directly physical disks rather than a loop file. Just format your disk and create an LVM partition, then pvcreate/ vgcreate - that one will remain active after you reboot the server 
 
Wouldn’t that work? Seems easier to me.
indded :)
 
Please advise.
 
Thanks,
Chris
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Regards,

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