Hi all,
I'm trying to set up DRBD to use with KVM virtual machines so that I can
have physical redundancy on my services. I followed this to use LVM
volumes as my DRBD backing device:
http://www.drbd.org/users-guide-8.3/s-lvm-lv-as-drbd-backing-dev.html
and then did this
http://www.drbd.org/users-guide-8.3/s-first-time-up.html to enable the
resource r0.
I did the initial device synchronization as per this:
http://www.drbd.org/users-guide-8.3/s-initial-full-sync.html and got the
expected results. I actually did this twice for 2 resources, it took a
while but eventually reported the 20GB volumes as:
root@kvm-srv-01:~# cat /proc/drbd
version: 8.3.11 (api:88/proto:86-96)
srcversion: 41C52C8CD882E47FB5AF767
1: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate C r-----
ns:0 nr:0 dw:0 dr:1220 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f
oos:0
2: cs:Connected ro:Secondary/Primary ds:UpToDate/UpToDate C r-----
ns:20970844 nr:0 dw:0 dr:20971696 al:0 bm:1280 lo:0 pe:0 ua:0
ap:0 ep:1 wo:f oos:0
and
root@kvm-srv-02:~# cat /proc/drbd
version: 8.3.11 (api:88/proto:86-96)
srcversion: 41C52C8CD882E47FB5AF767
1: cs:Connected ro:Secondary/Primary ds:UpToDate/UpToDate C r-----
ns:0 nr:0 dw:0 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:0
2: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate C r-----
ns:0 nr:20970844 dw:20970844 dr:672 al:0 bm:1280 lo:0 pe:0 ua:0
ap:0 ep:1 wo:f oos:0
The 2 resources are each to be used for testing guest Virtual Machine(s)
with KVM/DRBD. In the first instance I installed the guest before
creating the DRBD block device and after synchronization all the files
were available to use in a VM. In the second resource I created the
DRBD block device before installing the VM. I did this because I want
to be both creating new VMs and migrating existing ones to DRBD.
What I'm seeing is that changes to the primary do not seem to be on the
secondary. My understanding is that using Single Primary mode with
Protocol C should mean that all disk writes to the primary should be
complete after a successful write on the secondary.
If the writes are going to both nodes shouldn't I see non zero values
for Disk reads and Disk writes in /proc/drbd?
Perhaps the issue is that I'm using the LVM volumes directly for my KVM
VMs. I'm not sure if I should be approaching this with a nested
approach like this http://www.drbd.org/users-guide-8.3/s-nested-lvm.html
Does anyone have any thoughts on why my data doesn't seem to be
replicating or perhaps point me in the right direction for how to dig a
little deeper. My limited understanding is that DRBD should be between
my host and the LVM volume but perhaps it's writing directly to the LV
and not going through DRBD.
Thanks in advance.
--
*Paul O'Rorke*
Tracker Software Products
p...@tracker-software.com <mailto:paul.oro...@tracker-software.com>
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resource r0 {
device /dev/drbd1;
disk /dev/mapper/VirtualMachines-test;
meta-disk internal;
on kvm-srv-01 {
address 192.168.2.31:7789;
}
on kvm-srv-02 {
address 192.168.2.32:7789;
}
}resource r1 {
device /dev/drbd2;
disk /dev/VirtualMachines/test2;
meta-disk internal;
on kvm-srv-01 {
address 192.168.2.41:7789;
}
on kvm-srv-02 {
address 192.168.2.42:7789;
}
}
global {
usage-count yes;
# minor-count dialog-refresh disable-ip-verification
}
common {
protocol C;
handlers {
# The following 3 handlers were disabled due to #576511.
# Please check the DRBD manual and enable them, if they make
sense in your setup.
# pri-on-incon-degr "/usr/lib/drbd/notify-pri-on-incon-degr.sh;
/usr/lib/drbd/notify-emergency-reboot.sh; echo b > /proc/sysrq-trigger ; reboot
-f";
# pri-lost-after-sb "/usr/lib/drbd/notify-pri-lost-after-sb.sh;
/usr/lib/drbd/notify-emergency-reboot.sh; echo b > /proc/sysrq-trigger ; reboot
-f";
# local-io-error "/usr/lib/drbd/notify-io-error.sh;
/usr/lib/drbd/notify-emergency-shutdown.sh; echo o > /proc/sysrq-trigger ; halt
-f";
# fence-peer "/usr/lib/drbd/crm-fence-peer.sh";
# split-brain "/usr/lib/drbd/notify-split-brain.sh root";
# out-of-sync "/usr/lib/drbd/notify-out-of-sync.sh root";
# before-resync-target
"/usr/lib/drbd/snapshot-resync-target-lvm.sh -p 15 -- -c 16k";
# after-resync-target
/usr/lib/drbd/unsnapshot-resync-target-lvm.sh;
}
startup {
# wfc-timeout degr-wfc-timeout outdated-wfc-timeout
wait-after-sb
}
disk {
# on-io-error fencing use-bmbv no-disk-barrier no-disk-flushes
# no-disk-drain no-md-flushes max-bio-bvecs
}
net {
# sndbuf-size rcvbuf-size timeout connect-int ping-int
ping-timeout max-buffers
# max-epoch-size ko-count allow-two-primaries cram-hmac-alg
shared-secret
# after-sb-0pri after-sb-1pri after-sb-2pri data-integrity-alg
no-tcp-cork
}
syncer {
# rate after al-extents use-rle cpu-mask verify-alg csums-alg
}
}
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