[pve-devel] Error between PVE and LVM

[Cesar Peschiera]

Hi Alexandre

Thanks for your attention, here my answers and suggestions about of the
problem of your customer:

>We have made no change since resize feature has been implemented.
>Can you describe a little bit more the problem on the guest side ?
>do you see disk size increase with parted/fdisk ?
I see the new size (vm-100-disk-1) of the logical volume by CLI, but it
isn't reflected into the VM.
In my case DRBD is in a upper layer to the LV, but the concept of LVM is
applicable for any Logical Volume in any kind of block device that Linux can
recognise.
shell# lvs
LV VG Attr LSize Pool Origin Data%  Move Log Copy%  Convert
vm-100-disk-1 drbdvg2 -wi------  30.00g
data          pve     -wi-ao--- 143.50g
root          pve     -wi-ao---  20.00g
swap        pve     -wi-ao---  20.00g

>I have add a customer during a previous training session, which have
>problem with raw lvm disk in vms,
I don't have problems with the VMs (LVM or raw image file), only with the
LVM resize by CLI.

>because of proxmox host scanning all lvm disks on the host side. (Don't
>remember if it's have impact on resize).
It don't have impact on resize, and it is necessary for that LVM can manage 
the changes online included (VM and host), that it is my case.
Moreover, for my DRBD resources,  i use this filter on the lvm.conf file for 
avoid scanning all lvm disks:

filter = [ "r|/dev/sdb1|", "r|/dev/sdc1|", "r|/dev/sdd1|", "r|/dev/sde1|",
"r|/dev/disk/|", "r|/dev/block/|", "a/.*/" ]
Where:
a=accept (include) , and
r=reject (exclude) the scans to speed startup.

>We have need to add a filter in lvm.conf on the host, to exclude scan of
>vms lvm disk.
Sure, i use the CLI

An additional note of IBM:
In the best practices, LVM as block device is the mode more fast for get the
better performance in reads and writes of disks.

Official Web page of IBM in "Best practice: Use block devices for VM
storage":
http://www-01.ibm.com/support/knowledgecenter/linuxonibm/liaat/liaatbpblock.htm

And finally, my question:
Can be corrected my problem?

Best regards
Cesar

----- Original Message ----- 
From: "Alexandre DERUMIER" <aderumier at odiso.com>
To: "Cesar Peschiera" <brain at click.com.py>
Cc: <pve-devel at pve.proxmox.com>
Sent: Thursday, November 27, 2014 3:47 AM
Subject: Re: [pve-devel] Error between PVE and LVM


Hi,

>>In previous versions of PVE, this task was possible do it with much
>>easily.

We have made no change since resize feature has been implemented.
Can you describe a little bit more the problem on the guest side ?
do you see disk size increase with parted/fdisk ?

Do you use raw lvm disk in your vms ? or partitions on top of lvm ?
I have the LVM partition, and the image of the virtual disk isn't on a file
system (as raw, qcow2, or any other kind of file format), so my image disk
is a LVM as block device.

I have add a customer during a previous training session, which have problem
with raw lvm disk in vms,

because of proxmox host scanning all lvm disks on the host side. (Don't
remember if it's have impact on resize).

We have need to add a filter in lvm.conf on the host, to exclude scan of vms
lvm disk.

----- Mail original ----- 

De: "Cesar Peschiera" <brain at click.com.py>
À: pve-devel at pve.proxmox.com
Envoyé: Jeudi 27 Novembre 2014 07:15:19
Objet: [pve-devel] Error between PVE and LVM

Hi to the PVE team.

I found a problem between PVE and LVM.

Considering that if it is used LVM as block device for the virtual disks of
the VMs, Linux give us a great comfort, but the problem is that if I in
"online mode" enlarge a Physical Volume and after enlarge a Logical Volume
by CLI, in PVE, the VM can not see the new free hard disk space without
partition.

In previous versions of PVE, this task was possible do it with much easily.

Moreover, i think that this feature is very util, due to that in the actual
condition, it force me to power off the VM and start it again, so that being
a server (talking about of the VM) that is in a production environment, only
can I do it outside of working hours.

So i would like to ask if the PVE team have interest in correcting this
problem.

Best regards
Cesar

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