On 07/18/2014 05:43 PM, Andrew Lau wrote:
On Fri, Jul 18, 2014 at 10:06 PM, Vijay Bellur <vbel...@redhat.com
<mailto:vbel...@redhat.com>> wrote:
[Adding gluster-devel]
On 07/18/2014 05:20 PM, Andrew Lau wrote:
Hi all,
As most of you have got hints from previous messages, hosted
engine
won't work on gluster . A quote from BZ1097639
"Using hosted engine with Gluster backed storage is currently
something
we really warn against.
I think this bug should be closed or re-targeted at
documentation, because there is nothing we can do here. Hosted
engine assumes that all writes are atomic and (immediately)
available for all hosts in the cluster. Gluster violates those
assumptions.
"
I tried going through BZ1097639 but could not find much detail
with respect to gluster there.
A few questions around the problem:
1. Can somebody please explain in detail the scenario that causes
the problem?
2. Is hosted engine performing synchronous writes to ensure that
writes are durable?
Also, if there is any documentation that details the hosted engine
architecture that would help in enhancing our understanding of its
interactions with gluster.
Now my question, does this theory prevent a scenario of perhaps
something like a gluster replicated volume being mounted as a
glusterfs
filesystem and then re-exported as the native kernel NFS share
for the
hosted-engine to consume? It could then be possible to chuck
ctdb in
there to provide a last resort failover solution. I have tried
myself
and suggested it to two people who are running a similar
setup. Now
using the native kernel NFS server for hosted-engine and they
haven't
reported as many issues. Curious, could anyone validate my
theory on this?
If we obtain more details on the use case and obtain gluster logs
from the failed scenarios, we should be able to understand the
problem better. That could be the first step in validating your
theory or evolving further recommendations :).
I'm not sure how useful this is, but Jiri Moskovcak tracked this down
in an off list message.
Message Quote:
==
We were able to track it down to this (thanks Andrew for providing the
testing setup):
-b686-4363-bb7e-dba99e5789b6/ha_agent service_type=hosted-engine'
Traceback (most recent call last):
File
"/usr/lib/python2.6/site-packages/ovirt_hosted_engine_ha/broker/listener.py",
line 165, in handle
response = "success " + self._dispatch(data)
File
"/usr/lib/python2.6/site-packages/ovirt_hosted_engine_ha/broker/listener.py",
line 261, in _dispatch
.get_all_stats_for_service_type(**options)
File
"/usr/lib/python2.6/site-packages/ovirt_hosted_engine_ha/broker/storage_broker.py",
line 41, in get_all_stats_for_service_type
d = self.get_raw_stats_for_service_type(storage_dir, service_type)
File
"/usr/lib/python2.6/site-packages/ovirt_hosted_engine_ha/broker/storage_broker.py",
line 74, in get_raw_stats_for_service_type
f = os.open(path, direct_flag | os.O_RDONLY)
OSError: [Errno 116] Stale file handle:
'/rhev/data-center/mnt/localhost:_mnt_hosted-engine/c898fd2a-b686-4363-bb7e-dba99e5789b6/ha_agent/hosted-engine.metadata'
Andrew/Jiri,
Would it be possible to post gluster logs of both the mount and
bricks on the bz? I can take a look at it once. If I gather nothing then
probably I will ask for your help in re-creating the issue.
Pranith
It's definitely connected to the storage which leads us to the
gluster, I'm not very familiar with the gluster so I need to check
this with our gluster gurus.
==
Thanks,
Vijay
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