[ovirt-users] Recommended setup for a FC based storage domain

[combuster at archlinux.us]

One word of caution so far, when exporting any vm, the node that acts as SPM 
is stressed out to the max. I releived the stress by a certain margin with 
lowering libvirtd and vdsm log levels to WARNING. That shortened out the 
export procedure by at least five times. But vdsm process on the SPM node  is 
still with high cpu usage so it's best that the SPM node should be left with a 
decent CPU time amount to spare. Also, export of VM's with high vdisk capacity 
and thin provisioning enabled (let's say 14GB used of 100GB defined) took 
around 50min over a 10Gb ethernet interface to a 1Gb export NAS device that 
was not stressed out at all by other processes. When I did that export with 
debug log levels it took 5hrs :(

So lowering log levels is a must in production enviroment. I've deleted the 
lun that I exported on the storage (removed it first from ovirt) and for the 
next weekend I am planing to add a new one, export it again on all the nodes 
and start a few fresh vm installations. Things I'm going to look for are 
partition alignment and running them from different nodes in the cluster at 
the same time. I just hope that not all I/O is going to pass through the SPM, 
this is the one thing that bothers me the most.
 
I'll report back on these results next week, but if anyone has experience with 
this kind of things or can point  to some documentation would be great.

On Monday, 2. June 2014. 18.51.52 you wrote:
> I'm curious to hear what other comments arise, as we're analyzing a
> production setup shortly.
> 
> On Sun, Jun 1, 2014 at 10:11 PM,  <combuster at archlinux.us> wrote:
> > I need to scratch gluster off because setup is based on CentOS 6.5, so
> > essential prerequisites like qemu 1.3 and libvirt 1.0.1 are not met.
> 
> Gluster would still work with EL6, afaik it just won't use libgfapi and
> instead use just a standard mount.
> 
> > Any info regarding FC storage domain would be appreciated though.
> > 
> > Thanks
> > 
> > Ivan
> > 
> > On Sunday, 1. June 2014. 11.44.33 combuster at archlinux.us wrote:
> >> Hi,
> >> 
> >> I have a 4 node cluster setup and my storage options right now are a FC
> >> based storage, one partition per node on a local drive (~200GB each) and
> >> a
> >> NFS based NAS device. I want to setup export and ISO domain on the NAS
> >> and
> >> there are no issues or questions regarding those two. I wasn't aware of
> >> any
> >> other options at the time for utilizing a local storage (since this is a
> >> shared based datacenter) so I exported a directory from each partition
> >> via
> >> NFS and it works. But I am little in the dark with the following:
> >> 
> >> 1. Are there any advantages for switching from NFS based local storage to
> >> a
> >> Gluster based domain with blocks for each partition. I guess it can be
> >> only
> >> performance wise but maybe I'm wrong. If there are advantages, are there
> >> any tips regarding xfs mount options etc ?
> >> 
> >> 2. I've created a volume on the FC based storage and exported it to all
> >> of
> >> the nodes in the cluster on the storage itself. I've configured
> >> multipathing correctly and added an alias for the wwid of the LUN so I
> >> can
> >> distinct this one and any other future volumes more easily. At first I
> >> created a partition on it but since oVirt saw only the whole LUN as raw
> >> device I erased it before adding it as the FC master storage domain. I've
> >> imported a few VM's and point them to the FC storage domain. This setup
> >> works, but:
> >> 
> >> - All of the nodes see a device with the alias for the wwid of the
> >> volume,
> >> but only the node wich is currently the SPM for the cluster can see
> >> logical
> >> volumes inside. Also when I setup the high availability for VM's residing
> >> on the FC storage and select to start on any node on the cluster, they
> >> always start on the SPM. Can multiple nodes run different VM's on the
> >> same
> >> FC storage at the same time (logical thing would be that they can, but I
> >> wanted to be sure first). I am not familiar with the logic oVirt utilizes
> >> that locks the vm's logical volume to prevent corruption.
> >> 
> >> - Fdisk shows that logical volumes on the LUN of the FC volume are
> >> missaligned (partition doesn't end on cylindar boundary), so I wonder if
> >> this is becuase I imported the VM's with disks that were created on local
> >> storage before and that any _new_ VM's with disks on the fc storage would
> >> be propperly aligned.
> >> 
> >> This is a new setup with oVirt 3.4 (did an export of all the VM's on 3.3
> >> and after a fresh installation of the 3.4 imported them back again). I
> >> have room to experiment a little with 2 of the 4 nodes because currently
> >> they are free from running any VM's, but I have limited room for
> >> anything else that would cause an unplanned downtime for four virtual
> >> machines running on the other two nodes on the cluster (currently highly
> >> available and their drives are on the FC storage domain). All in all I
> >> have 12 VM's running and I'm asking on the list for advice and guidance
> >> before I make any changes.
> >> 
> >> Just trying to find as much info regarding all of this as possible before
> >> acting upon.
> >> 
> >> Thank you in advance,
> >> 
> >> Ivan
> > 
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