[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: [dm-devel] Use LVM on /dev/mapper/diskname and iSCSI



* S. J. van Harmelen

Thanks for your help!

I executed the pvs command and it did find a few partitions. I use
iSCSI to share the LUN's to a XenSource server, and XenSource creates
the PV's and LV's in order to provision VM's. Didn't think of that,
but that's on the disk of course.

Is there any way to configure snapshots for these already created LVM
partitions? Or do I have to whipe the disk clean (rather not do
that, but if I have to it can be done), then create the pv's and lv's
and then share the lv's true iSCSI?

In that case XenSource will again create pv's and lv's in the shared
lv. Ain't that a problem?

You really need a filter line in /etc/lvm/lvm.conf, to keep LVM from claiming 1) individual paths to a dm-multipath controlled LUN, and 2) LUNs that are PVs used by the LVM implementation in your domUs.

You don't want LVM to be claiming the paths directly, because you'd no longer have any redundancy - it will override dm-multipath. You also don't want the LVM implementation in your dom0 to be using the same block device as LVM in your domU as physical volumes, as LVM is designed to have exclusive access to its PVs (you might get around this with CLVM, though).

Do I understand correctly if you have one LUN that contains your domO (having its file systems in LVs), and several LUNs that contain your domUs, which again are PVs that are supposed to be used by your domU kernels?

If so you will want to keep your dom0 from claiming the domU PVs. Use a filter line that accepts only the multipath'ed volume that contains the dom0 installation, and drop the rest. For instance:

filter = [ "a|^/dev/mapper/domzero$", "r|.*" ]

...assuming your dom0 data volume is called "domzero" in multipath.conf.

Regards
--
Tore Anderson


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]