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From Stephan Seitz <s.se...@secretresearchfacility.com>
Subject Re: ACS 4.8 + Xen / XenServer + Ceph
Date Thu, 20 Oct 2016 15:41:24 GMT
Hi,

TL;DR; you can't. XenServer 6.5 just doesn't support RBD backends.

There are projects to integrate RBD-SR into XenServer 7, I don't know
if projects like https://github.com/rposudnevskiy/RBDSR will make it
into XenServer upstream.

A while ago, I closed that gap by using iSCSI in between. The slides
are in german, but I think the code snippets are easy to understand.

https://www.heinlein-support.de/sites/default/files/ceph-iscsi-host-fai
lover-multipath.pdf

That works and there are some XenServer Pools out there running on top
of ceph clusters.

Nowadays, I'ld try scst with replicated persistent reservations https:/
/github.com/bvanassche/scst/blob/master/scst/README.dlm backed on
kernel-mapped rbd's.

Anyway, If you're already running a ceph cluster, I'ld vote for KVM.

The bug you ran into is a pure ACS bug and afaik already fixed.

- Stephan


Am Donnerstag, den 20.10.2016, 15:22 +0200 schrieb (IMIS) Enzo Bettini:
> Hi,
> 
> I have been doing a lot of searching to find out or work out how to
> get 
> ACS 4.8 to work with XenServer 6.5 with a Ceph backend.
> Currently I am only able to find outdated articles with experimental 
> code being tested.
> 
> A little background:
> 
> We currently have a number of servers running CentOS 7 as KVM 
> hypervisors with ACS 4.8 installed on a separate server (also CentOS
> 7).
> The issue we have is that there is a bug in ACS where the disk cache 
> mechanism for virtual disks is not being pushed through to the
> database 
> or to the virtual machine.
> 
> Each host has 4 NICs. 2x 1Gbps and 2x 10Gbps.
> Each pair of NICs is bonded together. Public, Guest and Ceph traffic
> is 
> run on the 10Gbps bonded NICs.
> Management and ACS Storage traffic is run on the 1Gbps NICs.
> 
> We have been informed that this is working with XenServer? However,
> we 
> have been unable to get XenServer to play nice.
> After installing XenServer and updating the network so that we have 
> access to it. We are able to add the server to the XenServer cluster 
> which was created.
> But we are unable to deploy a VM on the newly added XenServer.
> 
> We have 2 primary storage options available. 1) NFS and 2) RBD.
> Neither 
> one of the two are working.
> We would prefer to use the RBD primary storage though.
> 
> The error we receive is that the host is unable to connect to
> primary 
> storage [ID].
> 
> Are there guides or steps available to get this working?
> 
> We have also attempted to use the Xen Hypervisor installed on CentOS
> 7 
> instead of XenServer, though that was until we read that ACS does
> not 
> support the Xen Hypervisor on its own and only supports XenServer
> 5.6 
> SP2 to 6.5 SP1.
> 
> Is XenServer the correct hypervisor to choose for an ACS and Ceph
> setup? 
> Or is there a more preferred hypervisor?
> 
> Regards,
> Enzo

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