Virtualization Plan Sanity Check

[Irazmus]

We are currently planning our first real foray into server virtualization and I'd appreciate a sanity check for our plans from someone who has more virtualization experience than me.

This is going to be a long one, so please bear with me.

History:
Over the last few years our server numbers have grown to the extent that we are over provisioned and most servers are under utilized (but have insufficient RAM for running multiple VMs). In addition, our SIMS and file servers (both Dell PowerEdge 2800s) are about to come out of warranty with no option to extend.

Due to local and national politics we are very short of money this year and cannot afford virtualization servers and to replace the file server.

What we can afford is to buy a server to start virtualizing and to move half the drives from our file server into our SIMS server and run the two machines as mirrored openfilers until we can afford a replacement next year.

For the VM host we're looking at buying an HP Proliant DL385

1 x AMD Opteron 6176SE (2.3GHz, 12 core) (Second socket for later expansion)
16 GB (8 x 2 GB RDIMM) Performance DDR3 RDIMM (256GB max)
4 x 600GB 6GB/s 10Krpm SAS DP (Expandable to 8)
OR
4 x 500GB 3GB/s 7.2Krpm SATA (Expandable to 8)

with a second to be bought in year 2 or 3 for redundancy. Until we buy the second, our existing servers will be used as backup VM hosts, with each being added to the cluster when it's current role is virtualized.

VMs will be stored on the VM host and mirrored to their backup machine with DRBD [ DRBD:What is DRBD ] to allow for failover without a SAN.

Virtualization will be provided by KVM on Debian (or possibly Gentoo), with Ganeti [ ganeti - Cluster-based virtualization management software - Google Project Hosting ] for VM management.

The VM's I intend to have running from this host are:

   HDD	Use			OS	RAM
-------------------------------------------------
 20GB	Host			Debian	1GB

 50GB	SIMS			W2K3	2GB
 20GB	DC			W2K3	1GB
 20GB	IIS			W2K3	1GB
 40GB	SuccessMaker		W2K3	1GB
100GB	WDS			W2K3	1GB
 15GB	Print			Debian	1GB
100GB	Webserver		Debian	2GB
 20GB	Proxy			*nix	2GB
 15GB	Intranet		Debian	512MB
 15GB	Syslog			Debian	512MB
240GB	Zimbra (e-Mail)		Debian	2GB

655GB	Total				15GB

with the possibility for separate MSSQL and MySQL hosts, and a puppet server further down the line.

----------------------------------------------------------------------------------------

Can anyone see any issues with this plan or am I actually managing to have a lucid moment?

[jamesb]

Looks reasonable enough to me. Cut a bit fine maybe, but reasonable.

Can your backup hypervisors support everything if the main hypervisor goes down? If not, have you given thought to which server roles you could afford to lose?

One other thought - do you have any other DCs or were you planning to cut down to just the one? Whether or not it's virtual, I'd recommend having a second one somewhere - it doesn't need to be a high spec, just needs to exist.

[sted]

can i suggest (assuming using hyperv on 08r2 as a host os) you give it 2gb ram of its own at least
does wds really need its own server seems a bit overkill for what is essentially a tftp server as it really has no impact on the server itself apart from the disk space it requires. Why not merge it wth the print server?

[FN-GM]

Can you merge SuccessMaker, Intranrt & syslog. This will free up some ram

[jamesb]

can i suggest (assuming using hyperv on 08r2 as a host os)

Main Page - KVM - KVM as host.

you give it 2gb ram of its own at least

Wouldn't hurt, but if you're having to be tight on resources probably not necessary. With Hyper-V yep.

does wds really need its own server seems a bit overkill for what is essentially a tftp server as it really has no impact on the server itself apart from the disk space it requires. Why not merge it wth the print server?

No need to combine servers - if you split the roles onto individual servers you can monitor their performance, and how much they actually use in terms of resources, and then lower what you're providing them with (or raise it) as time goes on in order to fine-tune the setup.

[glennda]

We currently use KVM on Ubuntu and its pretty good - i currently run 3 x DL380 G5 Dual Quad Xeon with 64GB ram in the main two and 12 in the backup - all connected via Fiber Channel to an MSA 2000. We use an Oracle Filesystem cluster for the San and these hosts run pretty much the entire network - the only problem i have is with file servers and thats because my San is not big enough to house the data (will be after summer when get extra enclosure)

I currently run about 20+ servers of varying roles on these hosts (mainly the two with 64gb ram in) cpu doesnt max about 40%

[sted]

No need to combine servers - if you split the roles onto individual servers you can monitor their performance, and how much they actually use in terms of resources, and then lower what you're providing them with (or raise it) as time goes on in order to fine-tune the setup.

granted but its still at last 20gb iirc used for a server08 install thats hard drive space for nothing and its still takes cpu cycles even if not many that could probably be better used elsewhere

[jamesb]

granted but its still at last 20gb iirc used for a server08 install thats hard drive space for nothing and its still takes cpu cycles even if not many that could probably be better used elsewhere

I may be too used to vSphere, but why would you have separate, full server images for each of your servers rather than having a single 'core' image with the base OS, then several separate linked clones with only the extra software installed on each?

[glennda]

can i suggest (assuming using hyperv on 08r2 as a host os) you give it 2gb ram of its own at least
does wds really need its own server seems a bit overkill for what is essentially a tftp server as it really has no impact on the server itself apart from the disk space it requires. Why not merge it wth the print server?

KVM out performs Server 2k8 and HyperV many times over IMHO

[sted]

I may be too used to vSphere, but why would you have separate, full server images for each of your servers rather than having a single 'core' image with the base OS, then several separate linked clones with only the extra software installed on each?

because as far as im aware thats how hyperv works the machines are 100% independant so you cant share core files

KVM out performs Server 2k8 and HyperV many times over IMHO

I have never used it so cant omment ive only really used hyperv, hyperv core(or whatever its called) and something else the name of which escapes me. My main reasn for liking hyperv is the fact you get an actual usable console on the host pc you dont need to rely on a 2nd machine to manage it

[plexer]

Are you planning on running virtualisation on you 2800's as the backup?

does kvm support those as I know hyper-v doesn't.

Ben

[Mr.Ben]

With the RAM requirements why not use the Hyper-V dynamic memory feature? (Introduced with 2008R2 SP1)

You could apply this to all non essential VM servers, allowing them to share a pool of Memory as and when they need it.

I would also combine some of those roles into single VM's.

[glennda]

Are you planning on running virtualisation on you 2800's as the backup?

does kvm support those as I know hyper-v doesn't.

Ben

if the cpu supports hardware virtualisation and also is x64 it should work AFAIK

[sted]

if the cpu supports hardware virtualisation and also is x64 it should work AFAIK

often needs a few option turned on in bios i know for instance hp g5 ml350s support it but you need to alter bios settings turn on virtualization and somthing else memory reaalted iirc (its been a while once i found out i enabled it on all my servers so if i ever wanted hyper v it was there)

[dhicks]

Over the last few years our server numbers have grown to the extent that we are over provisioned and most servers are under utilized (but have insufficient RAM for running multiple VMs).

For your older servers, double-check whether their processors have hardware support for virtualisation - you won't be able to use KVM on them if not. Xen will run paravirtualised (i.e. Linux-based) VMs on them, though, and you should be able to use Xen alongside KVM if you need to.

run the two machines as mirrored openfilers

Mirorred as in real-time (DRBD-style) mirrored? That's not a backup - delete a file from one and it deletes the same file from the other. I'd have your backup file server take a backup copy of your main file server once a day (or more often if you feel that's neccesary), storing several day's backups, and have the backup file server ready to take over as the file server if the first machine goes down for some reason. If you have a server outage (which should, hopefully, be very rare) people might loose a day's work, but I think having a versioned backup is more useful than a straight mirror.

VMs will be stored on the VM host and mirrored to their backup machine with DRBD

Good plan. Don't mirror your DC like this, though, use a secondary DC to mirror the first (you can still run them as virtual machines just fine, so you can move them around physical servers). Windows gets very confused if a previous backup of a domain controller is restarted, it's best to let active directory take care of mirroring itself.

Virtualization will be provided by KVM on Debian

I've had best results with Debian - my home servers are running Debian, it all seems very reliable.