KVM + LVM Questions

[J.R]

I'm currently testing ProxMox on a workstation and very impressed by it's features and the "clean" interface. Before I migrate our environment to ProxMox, I still have some questions about KVM in combination with LVM.

There's just one 160GB harddisk in my workstation (/dev/sda) fully claimed by the default PVE Volume Group on /dev/sda2 after install (besides the 504MB /boot volume on sda1). I couldn't find any possibility in the installer to configure the size of PVE Volume Group and/or three default Logical Volumes, so I ended up with the following disk layout:

root - 37,25GB
swap - 4GB
data - 103,26GB

1) How does the installer shares the available disk space ? A default Debian and/or ProxMox install needs less than 1GB, so I'm happy with a root volume that's something near 10GB (tmp, extra packages and other custom stuff). Even 10GB is overkill, but 37,25GB ???

2) I like to use KVM with native LVM Logical Volumes as disks, not image files (raw, qcow). Am I right that using this "simple" test workstation with only one disk (that's fully claimed by the default PVE Volume Group) is limiting this possibility ? In other words, when I do have extra disks (sdb, sdc, etc + additional Volume Groups) this should be possible ?
My production servers all have RAID adapters capable of creating multiple volumes on a single RAID set, by creating these multiple RAID volumes I end up with corresponding SCSI devices (sda, sdb, etc). Can anyone confirm this should be the way to go so the installer only claims /dev/sda and I can limit the PVE Volume Group to the size of this device ?


Although I didn't try it yet, I could customize the above default LVM layout created with the installer by resizing filesystems, create an additional partition (/dev/sda3) for an extra Volume Group designated for KVM logical Volumes. Also the installer "just" leaves 4GB of unclaimed space in the PVE Volume Group (that can be used by snapshots) that I like to change for some custom backup stuff.

In short , it should be great if the installer gives me the opportunity to let me choose between a default or custom LVM configuration. Is this already a wishlist item ?

 

[udo]

I'm currently testing ProxMox on a workstation and very impressed by it's features and the "clean" interface. Before I migrate our environment to ProxMox, I still have some questions about KVM in combination with LVM.

There's just one 160GB harddisk in my workstation (/dev/sda) fully claimed by the default PVE Volume Group on /dev/sda2 after install (besides the 504MB /boot volume on sda1). I couldn't find any possibility in the installer to configure the size of PVE Volume Group and/or three default Logical Volumes, so I ended up with the following disk layout:

root - 37,25GB
swap - 4GB
data - 103,26GB

1) How does the installer shares the available disk space ? A default Debian and/or ProxMox install needs less than 1GB, so I'm happy with a root volume that's something near 10GB (tmp, extra packages and other custom stuff). Even 10GB is overkill, but 37,25GB ???

2) I like to use KVM with native LVM Logical Volumes as disks, not image files (raw, qcow). Am I right that using this "simple" test workstation with only one disk (that's fully claimed by the default PVE Volume Group) is limiting this possibility ? In other words, when I do have extra disks (sdb, sdc, etc + additional Volume Groups) this should be possible ?
My production servers all have RAID adapters capable of creating multiple volumes on a single RAID set, by creating these multiple RAID volumes I end up with corresponding SCSI devices (sda, sdb, etc). Can anyone confirm this should be the way to go so the installer only claims /dev/sda and I can limit the PVE Volume Group to the size of this device ?


Although I didn't try it yet, I could customize the above default LVM layout created with the installer by resizing filesystems, create an additional partition (/dev/sda3) for an extra Volume Group designated for KVM logical Volumes. Also the installer "just" leaves 4GB of unclaimed space in the PVE Volume Group (that can be used by snapshots) that I like to change for some custom backup stuff.

In short , it should be great if the installer gives me the opportunity to let me choose between a default or custom LVM configuration. Is this already a wishlist item ?

Hi,
you can limit your root-size with maxroot - see posting http://forum.proxmox.com/threads/3424-Large-pve-root?p=19195#post19195
To use lvm for VMs it makes more sense with volume groups on a shared storage (iscsi, fc-raid...) and not local. With external storage you are able to use live-migration - this is very usefull.
But you can use your raid-slices for drbd (see wiki) and use that for lvm and live-migration. But test it before (performance and so on).

Udo

 

[tom]

I'm currently testing ProxMox on a workstation and very impressed by it's features and the "clean" interface. Before I migrate our environment to ProxMox, I still have some questions about KVM in combination with LVM.

There's just one 160GB harddisk in my workstation (/dev/sda) fully claimed by the default PVE Volume Group on /dev/sda2 after install (besides the 504MB /boot volume on sda1). I couldn't find any possibility in the installer to configure the size of PVE Volume Group and/or three default Logical Volumes, so I ended up with the following disk layout:



1) How does the installer shares the available disk space ? A default Debian and/or ProxMox install needs less than 1GB, so I'm happy with a root volume that's something near 10GB (tmp, extra packages and other custom stuff). Even 10GB is overkill, but 37,25GB ???

root - 37,25GB
swap - 4GB
data - 103,26GB

See http://forum.proxmox.com/threads/1874-How-to-specify-maxroot-in-a-simpler-way..?p=10003#post10003

but it makes sense to have space in root, e.g. if you want to make snapshots (vzdump) to the local disks.

2) I like to use KVM with native LVM Logical Volumes as disks, not image files (raw, qcow). Am I right that using this "simple" test workstation with only one disk (that's fully claimed by the default PVE Volume Group) is limiting this possibility ? In other words, when I do have extra disks (sdb, sdc, etc + additional Volume Groups) this should be possible ?

yes, see http://pve.proxmox.com/wiki/Storage_Model

My production servers all have RAID adapters capable of creating multiple volumes on a single RAID set, by creating these multiple RAID volumes I end up with corresponding SCSI devices (sda, sdb, etc). Can anyone confirm this should be the way to go so the installer only claims /dev/sda and I can limit the PVE Volume Group to the size of this device ?

the installer take one volume, e.g. /dev/sda. you can select this during installation. so you can install on sda, and configure later manually sdb as LVM.

Although I didn't try it yet, I could customize the above default LVM layout created with the installer by resizing filesystems, create an additional partition (/dev/sda3) for an extra Volume Group designated for KVM logical Volumes. Also the installer "just" leaves 4GB of unclaimed space in the PVE Volume Group (that can be used by snapshots) that I like to change for some custom backup stuff.

In short , it should be great if the installer gives me the opportunity to let me choose between a default or custom LVM configuration. Is this already a wishlist item ?

if you cannot live with the these defaults (I assume you can), you have still the possibility to install a Debian Lenny and on top Proxmox VE, see http://pve.proxmox.com/wiki/Install_Proxmox_VE_on_Debian_Lenny

It looks that you know Debian/Linux so this would be any easy task for you, giving all flexibility.

 

[J.R]

Tnx for answering Udo & Tom, just the info I needed. (And will read the WiKi better ;-))

I'm aware that my suggested setup only makes sense in a (single disk) test environment, in production my KVM virtual machine LVM's will be on shared storage. Beginning to understand ProxMox bit-by-bit...