[DRBD-user] Understanding "classic" 3 node set up.
Paul O'Rorke
paul at tracker-software.com
Mon Feb 5 19:27:31 CET 2018
Moving ahead with the assumptions before and I have defined the stacked
resource on node "alice" (trk-kvm-01), created the drbd block device:
root at trk-kvm-01:~# drbdadm create-md --stacked convirt-U
md_offset 53685411840
al_offset 53685379072
bm_offset 53683740672
Found some data
==> This might destroy existing data! <==
Do you want to proceed?
[need to type 'yes' to confirm] yes
initializing activity log
NOT initializing bitmap
Writing meta data...
New drbd meta data block successfully created.
success
It comes up OK:
root at trk-kvm-01:~# drbdadm up --stacked convirt-U
root at trk-kvm-01:~# drbd-overview
...
12:convirt/0 Connected Primary/Secondary
UpToDate/UpToDate _convirt vda virtio
...
120:convirt-U/0 ^^12 Connected Secondary/Secondary
Inconsistent/Diskless
I made it the primary
root at trk-kvm-01:~# drbdadm primary --force --stacked convirt-U
It seems OK on this node:
root at trk-kvm-01:~# drbd-overview
...
12:convirt/0 Connected Primary/Secondary
UpToDate/UpToDate _convirt vda virtio
...
120:convirt-U/0 ^^12 Connected Primary/Secondary
UpToDate/Diskless
However when I try to create the drbd block device on the third node I
get the following:
root at trk-kvm-03:~# drbdadm create-md convirt-U
open(inetrnal) failed: No such file or directory
open(inetrnal) failed: No such file or directory
Command 'drbdmeta 120 v08 inetrnal flex-external create-md'
terminated with exit code 20
What file is it looking for that it fails to find?
The resource is defined with this:
resource convirt {
net {
protocol C;
}
device /dev/drbd12;
meta-disk internal;
on trk-kvm-01 {
address 10.10.0.85:7789;
disk /dev/trk-kvm-01-vg/convirt;
}
on trk-kvm-02 {
address 10.10.0.86:7789;
disk /dev/trk-kvm-02-vg/convirt;
}
}
resource convirt-U {
net {
protocol A;
}
stacked-on-top-of convirt {
device /dev/drbd120;
address 192.168.0.101:7789;
}
on trk-kvm-03 {
device /dev/drbd120;
disk /dev/trk-kvm-03-vg/convirt;
address 192.168.0.201:7899;
meta-disk inetrnal;
}
}
The underlying LVM volume does exist:
root at trk-kvm-03:~# lvs
LV VG Attr LSize Pool Origin
Data% Meta% Move Log Cpy%Sync Convert
...
convirt trk-kvm-03-vg -wi-a----- 50.00g
...
I tried removing the volume with lvremove:
root at trk-kvm-03:~# lvremove /dev/trk-kvm-03-vg/convirt
Do you really want to remove and DISCARD active logical volume
convirt? [y/n]: y
Logical volume "convirt" successfully removed
and creating it again with lvcreate:
root at trk-kvm-03:~# lvcreate -L50G -n convirt trk-kvm-03-vg
Logical volume "convirt" created.
it looks OK
--- Logical volume ---
LV Path /dev/trk-kvm-03-vg/convirt
LV Name convirt
VG Name trk-kvm-03-vg
LV UUID QT7YNm-zlYi-7S0d-lF26-EEi2-7g69-0iU3aC
LV Write Access read/write
LV Creation host, time trk-kvm-03, 2018-02-05 09:03:56 -0800
LV Status available
# open 0
LV Size 50.00 GiB
Current LE 12800
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 252:13
Why can I not make the DRBD block device? I see that some required file
is missing but I don't understand what:
root at trk-kvm-03:~# drbd-overview
120:convirt-U/0 . . .
and
root at trk-kvm-03:~# cat /proc/drbd
version: 8.4.5 (api:1/proto:86-101)
srcversion: 4B3E2E2CD48CAE5280B5205
120: cs:Unconfigured
Something simple I have missed/misunderstood?
*Paul O'Rorke*
*Tracker Software Products (Canada) Limited *
www.tracker-software.com <http://www.tracker-software.com/>
Tel: +1 (250) 324 1621
Fax: +1 (250) 324 1623
<http://www.tracker-software.com/>
Support:
http://www.tracker-software.com/support
Download latest Releases
http://www.tracker-software.com/downloads/
On 2018-02-02 11:31 AM, Paul O'Rorke wrote:
>
> Hi
>
> I hope this is the right place to ask what may be a silly question. I
> have searched the archives and still do not understand properly how to
> set up "classic 3 node" for DR.
>
> I have been using a simple HA setup for some years now for KVM virtual
> machines. I have a DRBD resource for each VM, backed by LVM volumes,
> each using a unique IP (aliases) via CAT5 directly connecting
> dedicated NICs on each of "alice" and "bob" (I'm using the example
> from the docs here for simplicity). I run half the guests on each
> host and manually fail over if it is ever needed. This has been rock
> solid for me, great performance and has on more than one occasion
> saved my bacon. I want to set up a classic 3 node DR with a VPN
> connected off site 3rd stacked node.
>
> Referring to this
> http://docs.linbit.com/docs/users-guide-8.4/#s-three-nodes 6.18.2.
> Configuring a stacked resource
>
> I don't understand where to set up the interface for the stacked resource:
>
> |stacked-on-top-of r0 { device /dev/drbd10; address 192.168.42.1:7788; }|
>
> What interface gets this IP? I am assuming it goes on the primary
> node of the lower resource. So for the example in the docs, if alice
> is the primary I set up 192.168.42.1:7789 on alice and if I have to
> switch bob to primary I loose replication to charlie until such time
> as I either restore alice as the primary or can I set up
> 192.168.42.1:7789 on bob somehow and continue off site replication
> while alice is down?
>
> As I am reading it bob has no "knowledge" of charlie and the upper
> resource can only function while alice is primary. Is that right?
>
> Sorry if this is explained somewhere and I missed it.
>
> regards
>
> --
>
> *Paul O'Rorke*
> *Tracker Software Products (Canada) Limited *
> www.tracker-software.com <http://www.tracker-software.com/>
> Tel: +1 (250) 324 1621
> Fax: +1 (250) 324 1623
>
> <http://www.tracker-software.com/>
>
> Support:
> http://www.tracker-software.com/support
> Download latest Releases
> http://www.tracker-software.com/downloads/
>
>
>
>
>
>
> _______________________________________________
> drbd-user mailing list
> drbd-user at lists.linbit.com
> http://lists.linbit.com/mailman/listinfo/drbd-user
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