Re: [ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster?
- Original Message - From: Andrew Lau and...@andrewklau.com To: users users@ovirt.org Sent: Friday, July 18, 2014 4:50:31 AM Subject: [ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster? 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. My current setup is hosted engine, configured w/ gluster storage as described in my blog post, but with three hosts and replica 3 volumes. Only issue I've seen is an errant message about the Hosted Engine being down following an engine migration. The engine does migrate successfully, though. RE your bug, what do you use for a mount point for the nfs storage? Jason 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. Until the documentation gets updated, I hope this serves as a useful notice at least to save people some of the headaches I hit like hosted-engine starting up multiple VMs because of above issue. 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? Thanks, Andrew ___ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users ___ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users
Re: [ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster?
- Original Message - From: Jason Brooks jbro...@redhat.com To: Andrew Lau and...@andrewklau.com Cc: users users@ovirt.org Sent: Tuesday, July 22, 2014 8:29:46 AM Subject: Re: [ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster? - Original Message - From: Andrew Lau and...@andrewklau.com To: users users@ovirt.org Sent: Friday, July 18, 2014 4:50:31 AM Subject: [ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster? 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. My current setup is hosted engine, configured w/ gluster storage as described in my blog post, but with three hosts and replica 3 volumes. Only issue I've seen is an errant message about the Hosted Engine being down following an engine migration. The engine does migrate successfully, though. RE your bug, what do you use for a mount point for the nfs storage? In the log you attached to your bug, it looks like you're using localhost as the nfs mount point. I use a dns name that resolves to the virtual IP hosted by ctdb. So, you're only ever talking to one nfs server at a time, and failover between the nfs hosts is handled by ctdb. Anyway, like I said, my main testing rig is now using this configuration, help me try and break it. :) Jason 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. Until the documentation gets updated, I hope this serves as a useful notice at least to save people some of the headaches I hit like hosted-engine starting up multiple VMs because of above issue. 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? Thanks, Andrew ___ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users ___ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users ___ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users
Re: [ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster?
On 23/07/2014 1:45 am, Jason Brooks jbro...@redhat.com wrote: - Original Message - From: Jason Brooks jbro...@redhat.com To: Andrew Lau and...@andrewklau.com Cc: users users@ovirt.org Sent: Tuesday, July 22, 2014 8:29:46 AM Subject: Re: [ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster? - Original Message - From: Andrew Lau and...@andrewklau.com To: users users@ovirt.org Sent: Friday, July 18, 2014 4:50:31 AM Subject: [ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster? 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. My current setup is hosted engine, configured w/ gluster storage as described in my blog post, but with three hosts and replica 3 volumes. Only issue I've seen is an errant message about the Hosted Engine being down following an engine migration. The engine does migrate successfully, though. That was fixed in 3.4.3 I believe, although when it happened to me my engine didn't migrate it just sat there. RE your bug, what do you use for a mount point for the nfs storage? In the log you attached to your bug, it looks like you're using localhost as the nfs mount point. I use a dns name that resolves to the virtual IP hosted by ctdb. So, you're only ever talking to one nfs server at a time, and failover between the nfs hosts is handled by ctdb. I also tried your setup, but hit other complications. I used localhost in an old setup, previously as I was under the assumption when accessing anything gluster related, the connection point only provides the volume info and you connect to any server in the volume group. Anyway, like I said, my main testing rig is now using this configuration, help me try and break it. :) rm -rf / Jokes aside, are you able to reboot a server without losing the VM ? My experience with ctdb (based on your blog) was even with the floating/virtual IP it wasn't fast enough, or something in the gluster layer delayed the failover. Either way, the VM goes into paused state and can't be resumed. Jason 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. Until the documentation gets updated, I hope this serves as a useful notice at least to save people some of the headaches I hit like hosted-engine starting up multiple VMs because of above issue. 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? Thanks, Andrew ___ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users ___ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users ___ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users
Re: [ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster?
RE your bug, what do you use for a mount point for the nfs storage? In the log you attached to your bug, it looks like you're using localhost as the nfs mount point. I use a dns name that resolves to the virtual IP hosted by ctdb. So, you're only ever talking to one nfs server at a time, and failover between the nfs hosts is handled by ctdb. I also tried your setup, but hit other complications. I used localhost in an old setup, previously as I was under the assumption when accessing anything gluster related, the connection point only provides the volume info and you connect to any server in the volume group. As I understand it, with Gluster's nfs, the server you mount is the only one you're accessing directly, which is why you need to use something else to distribute the load, like round robin dns, with gluster's nfs. Anyway, like I said, my main testing rig is now using this configuration, help me try and break it. :) rm -rf / Jokes aside, are you able to reboot a server without losing the VM ? My experience with ctdb (based on your blog) was even with the floating/virtual IP it wasn't fast enough, or something in the gluster layer delayed the failover. Either way, the VM goes into paused state and can't be resumed. I have rebooted my hosts without issue. If I want to reboot the host that's serving the nfs storage, I've stopped ctdb first on that host, to make it hand off the nfs -- I've done this out of caution, but I should try just pulling the plug, too. The main source of VM pausing I've seen is when you have two nodes, one goes down, and the gluster quorum business goes into effect. With my current 3 node, replica 3 setup, gluster stays happy wrt quorum. I'll be sure to post about it if I have problems, but it's been working well for me. Jason ___ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users
[ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster?
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. Until the documentation gets updated, I hope this serves as a useful notice at least to save people some of the headaches I hit like hosted-engine starting up multiple VMs because of above issue. 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? Thanks, Andrew ___ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users
Re: [ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster?
[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 :). Thanks, Vijay ___ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users
Re: [ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster?
On Fri, Jul 18, 2014 at 10:06 PM, Vijay Bellur 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/localho st:_mnt_hosted-engine/c898fd2a-b686-4363-bb7e-dba99e5789b6/ha_agent/hosted- engine.metadata' 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 ___ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users
