On 20/10/13 02:22, John R Pierce wrote:
> In our development lab, I am installing 4 new servers, that I want to
> use for hosting KVM. each server will have its own direct attached
> raid. I'd love to be able to 'pool' this storage, but over gigE, I
> probably shouldn't even try.
I've build DRBD-backed shared storage using 1 Gbit network for
replication for years and the network has not been an issue. So long as
your apps can work with ~110 MB/sec max throughput, you're fine.
Latency is not effected because the average seek time of a platter, even
15krpm SAS drives, it higher than the network latency (assuming decent
equipment).
> most of the VM's will be running CentOS 5 and 6, some of the VM's will
> be postgresql database dev/test servers, others will be running java
> messaging workloads, and various test jobs.
>
> to date, my experience with KVM is bringing up one c6 VM on a c6 host,
> manually w/ virt-install and virsh...
>
> stupid questions ...
>
> whats the best storage setup for KVM when using direct attached raid?
> surely using disk image files on a parent ext4/xfs file system isn't the
> best performance? Should I use host lvm logical volumes as guest
> vdisks? we're going to be running various database servers in dev/test
> and wanting at least one or another at a time to really be able to get
> some serious iops.
What makes the most difference is not the RAID configuration but having
batery-backed (or flash-backed) write caching. With multiple VMs having
high disk IO, it will get random in a hurry. The caching allows for
keeping the systems responsive even under these highly random writes.
As for the storage type; I use clustered LVM (with DRBD as the PVs) and
give each VM a dedicated LV, as you mentioned above. This takes the FS
overhead out of the equation.
> its virt-manager worth using, or is it too simplistic/incomplete ?
I use it from my laptop, via an ssh tunnel, to the hosts all the time. I
treat it as a "remote KVM" switch as it gives me access to the VMs
regardless of their network state. I don't use it for anything else.
> will virt-manager or some other tool 'unify' management of these 4 VM
> hosts, or will it be pretty much, me-the-admin keeps track of what vm is
> on what host and runs the right virt-manager and manages it all fairly
> manually?
Depends what you mean by "manage" it. You can use 'virt-manager' on your
main computer to connect to the four hosts (and even set them to
auto-connect on start). From there, it's trivial to boot/connect/shut
down the guests.
If you're looking for high-availability of your VMs (setting up your
servers in pairs), this might be of interest;
https://alteeve.ca/w/2-Node_Red_Hat_KVM_Cluster_Tutorial
--
Digimer
Papers and Projects: https://alteeve.ca/w/
What if the cure for cancer is trapped in the mind of a person without
access to education?
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