[DRBD-user] DRBD + LVM

Mike Hall MHall at astc.nt.gov.au
Thu Sep 2 02:15:58 CEST 2010

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

I'm currently testing a replicated network storage device using CentOS 5.5 and DRBD 8.3, as a storage back end for KVM virtualisation. We may use either iSCSI (~SAN) or NFS (~NAS) to make this storage available to the VM host.

I was having trouble changing the status of a DRBD node or bringing a node off-line, getting messages about something holding the device open. This turned out to be LVM, and it appears that it is necessary to bring LVM volumes offline (vgchange -an) before changing DRBD's status.

So, my question is this:

If I bring LVM volumes offline on node 1 and demote node 1 to secondary, then promote node 2 to primary and bring the LVM volumes online again on node 2, is it necessary to also bring those LVM volumes online again back on node 1?

I'm guessing no (because it's the 'same' device on either node), but am checking to be sure.

Also, it it better to:

- format the LVMs on the storage machine (NAS/SAN) and then make those volumes available to the VM host, or

- in the case of iSCSI, just make unformatted devices available and format them from the VM host?

Anything else I need to be aware of ?


Michael Hall
IT Communications Officer
Alice Springs Town Council
mhall at astc.nt.gov.au
(08) 8950 0561

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