Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
> > Message: 1 > Date: Thu, 4 Mar 2010 17:48:24 +0100 > From: Olivier LAMBERT <lambert.olivier at gmail.com> > Subject: [DRBD-user] Detection of Logical Volume on nested LVM > replication > To: drbd-user at lists.linbit.com > Message-ID: > <f769216c1003040848m4b1ffaaatc15dc952781ce946 at mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > Hello, > > I'll try to be clear, but it's really hard to explain.. > In few words : when I create a Logical Volume on a host attached > (iSCSI) to one DRBD server, it doesn't appear on the second host, > attached to the other DRBD. But, on existing LV, it works like a charm > (all data's are replicated). And more, if I create a LV on "one side", > and fill it with data, I saw the replication link with heavy traffic, > but always no LV. > Now, to understand, here is how it happened with this infrastructure. > > 1) On both DRBD hosts : Debian GNU/Linux, Dual Primary setup, version: > 8.3.7 (api:88/proto:86-91). I choose to configure a resource on a > Logical volume of 500Gb (named /dev/vg0/xen). To be clear, two hosts > are "DRBD1" & "DRBD2". a cat /proc/drbd gave this : > 0: cs:Connected ro:Primary/Primary ds:UpToDate/UpToDate C r---- > ns:153716 nr:408752 dw:562408 dr:355156 al:179 bm:109 lo:0 pe:0 > ua:0 ap:0 ep:1 wo:n oos:0 > > > 2) This resource is exported with iSCSI. For the example, let's say > that CLIENT1 is connected to DRBD1, and CLIENT2 is connected to DRBD2. > It's simplifed because in real, it's multiple Xen Dom0's clients with > multipath (but we don't care of that here). > > 3) CLIENT1 see the device as a block device (so far so good, iSCSI > works). I choose to use LVM on this block device. I create for example > : /dev/vg_xen/mydisk on CLIENT1. I mount it, I put some stuff in there > : I saw the replication like working : some traffic. DRBD2 and 1 says > it's all OK. If I lvscan on CLIENT1, I can see my brand new volume. > > 4) CLIENT2, (so, connected on iSCSI with DRBD2), see the block device, > the volume group, but NOT the Logical Volume. If I disconnect DRBD2's > resource, and reconnect it, and reconnect iSCSI of CLIENT2, wow, I saw > the LV ! > > And more : if the LV exists on both side (after disconnect/reconnect > the resource), data's are correctly replicated (obviously, I do NOT > mount LV on both side, I'm aware of that !). But, if I fill on one > side (e.g CLIENT1), dismount it, then mount it on CLIENT2, data are > here, without any problem. > > So, my "theory", is that LVM operations (lvcreate or lvremove) on a > volume group, which is on top of iSCSI and LVM replicated device by > DRBD, are NOT replicated, UNTIL disconnect/reconnect the ressource. I > don't know why, and that's why I ask here to understand what I miss. Right. Discussed many times here and on Heartbeat/Pacemaker list. Try to search with cLVM keyword. > Additional Informations: If my clients are connected to the SAME DRBD > (let's tell DRBD1), if CLIENT1 creates a LV, CLIENT2 is immediatly > aware of that (just inactive, not a problem, vgchange and it works). > So the "problem" is during the replication. > > Thanks for your help. > > > Regards, > > > Olivier > XO Project > http://xen-orchestra.com >