Am 24.06.2011 um 16:58 schrieb Whit Blauvelt:
I truly appreciate that, Pete. What I've been hoping to find is
distribution-neutral models for handling KVM failover, where each
KVM VM is
directly on top of a dedicated DRBD resource - which is a setup with
an
ideal granularity, as compared to having multiple VMs sharing a
single DRBD
resource. Because the granularity is right-sized, it greatly
simplifies the
possible failure modes, and what should be needed for reliable
failover. For
example, if it were one shared DRBD resource for many VMs running
across two
hosts, it would need to run primary-primary, with CLVM and a
clustering file
system and the full pacemaker-corosync/heartbeat treatment. I get
that. But
with dedicated, per-VM DRBD resources, each can be run primary-
secondary (if
you don't mind a few seconds down during migration - which will be
there in
failover in any case), so there's no need for CLVM or one of the (less
mature than ext4 or xfs) clustering file systems in the arrangement.
ACK. Such a configuration should be usual and wide-spread:
A two node cluster with some VMs running criss-cross, each on a
dedicated Primary/secondary DRBD resource.
One can do it with KVM or Xen or something similar, Primary/Primary
with live-migration, or Primary/Secondary without.
IMHO it is a very common configuration.
There also should be a whole lot less needed on the pacemaker-
corosync/heartbeat side. What I've been hoping to find is
documentation on
just enough of pacemaker-corosync/heartbeat to handle this simplified
architecture adequately. But most of the documentation isn't aimed
towards
an architecture like this at all, and just about nothing I've found
addresses a KVM environment.
I join in ranting: there is a lot docs and HOWTOs out there, but
nothing of sufficient quality.
It still needs many hours (days) of trial and error.
Here is my crm conf for a similar XEN on dedicated DRBD (shortened to
two VMs):
node $id="..." xen11
node $id="..." xen10
primitive xen_cmsdb ocf:heartbeat:Xen \
params xmfile="/etc/xen/cmsdb.cfg" \
op monitor interval="3s" timeout="30s" \
op start interval="0" timeout="60s" \
op stop interval="0" timeout="40s" \
meta target-role="Started" allow-migrate="false"
primitive xen_www ocf:heartbeat:Xen \
params xmfile="/etc/xen/www.cfg" \
op monitor interval="3s" timeout="30s" \
op start interval="0" timeout="60s" \
op stop interval="0" timeout="40s" \
meta target-role="started" allow-migrate="false"
primitive xen_drbd1_1 ocf:linbit:drbd \
params drbd_resource="drbd1_1" \
op monitor interval="15s" \
op start interval="0" timeout="240s" \
op stop interval="0" timeout="100s"
primitive xen_drbd1_2 ocf:linbit:drbd \
params drbd_resource="drbd1_2" \
op monitor interval="15s" \
op start interval="0" timeout="240s" \
op stop interval="0" timeout="100s"
primitive xen_drbd5_1 ocf:linbit:drbd \
params drbd_resource="drbd5_1" \
op monitor interval="15s" \
op start interval="0" timeout="240s" \
op stop interval="0" timeout="100s"
primitive xen_drbd5_2 ocf:linbit:drbd \
params drbd_resource="drbd5_2" \
op monitor interval="15s" \
op start interval="0" timeout="240s" \
op stop interval="0" timeout="100s"
group group_drbd1 xen_drbd1_1 xen_drbd1_2
group group_drbd5 xen_drbd5_1 xen_drbd5_2
ms DrbdClone1 group_drbd1 \
meta master_max="1" master-mode-max="1" clone-max="2" clone-
node-max="1" notify="true"
ms DrbdClone5 group_drbd5 \
meta master_max="1" master-mode-max="1" clone-max="2" clone-
node-max="1" notify="true"
location cli-prefer-xen_cmsdb xen_cmsdb \
rule $id="cli-prefer-rule-xen_cmsdb" inf: #uname eq xen10
location cli-prefer-xen_www xen_www \
rule $id="cli-prefer-rule-xen_www" inf: #uname eq xen11
location prefer_xen10_cmsdb xen_cmsdb 50: xen10
location prefer_xen10_www xen_www 40: xen10
location prefer_xen11_cmsdb xen_cmsdb 40: xen11
location prefer_xen11_www xen_www 50: xen11
colocation xen_cmsdb_and_drbd inf: xen_cmsdb DrbdClone5:Master
colocation xen_www_and_drbd inf: xen_www DrbdClone1:Master
order xen_cmsdb_after_drbd inf: DrbdClone5:promote xen_cmsdb:start
order xen_www_after_drbd inf: DrbdClone1:promote xen_www:start
property $id="cib-bootstrap-options" \
dc-version="1.0.9-74392a28b7f31d7ddc86689598bd23114f58978b" \
cluster-infrastructure="Heartbeat" \
stonith-enabled="false" \
no-quorum-policy="ignore" \
last-lrm-refresh="1309523267"
rsc_defaults $id="rsc-options" \
resource-stickiness="100"
HTH
Helmut Wollmersdorfer
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