Zimba Multi-Install Virtualization

[Roturgo]

We're considering setting up multiple virtual Zimbra NE installs on a single (beefy) server vs. going with multiple single instance Zimbra installs on separate (smaller) servers. I've done some research on the issue, but most all virtualization topics have only covered a single virtualized instance of Zimbra.

My question is, has anyone else done multiple virtualized instances of Zimbra on a single server? If so, what was your experience? How big of a box did you use, and how well did Zimbra scale in that environment?

We're thinking of spending about $4,000 - $5,0000 on a single virtualization beefy server (SAS, RAID 10, Dual Quad Core Xeon, ~12 GB RAM, VMware Server or VMware ESX Server) as opposed to 6 or so ~$2000 single instance servers.

Thanks in advance for any input!

[fcash]

We haven't done this yet, but our plan is to put our Zimbra install into a Xen VM on the following hardware:

Tyan Thunder K8SD-Pro (S2882) motherboard
2x AMD Opteron 200-series single core CPUs ~2 GHz
8 GB DDR400 ECC RAM
3Ware Escalade 9550SX-12ML SATA RAID controller
12x 400 GB SATA-II HD

Just waiting for a replacement CPU to arrive. Then we'll be putting Ubuntu Server 7.10 (64-bit) on there as the Xen dom0, and putting Zimbra into an Ubuntu 6.06 LTS (32-bit) Xen domU.

Depending on how the CPU/RAM/HD/NIC usage is, we may be moving our old webmail system into a Xen VM, as well as our old FirstClass server. Keep all our e-mail systems virtualised on a single box (until we finish the user migration to Zimbra, that is).

We've had good experience with Xen 3 in the past (Debian Linux 4.0 dom0) on similar hardware for file/print servers and web server. We're putting together a larger box (Tyan h2000M motherboard, 2x AMD Opteron 2000-series dual-core CPUs) to take over for a bunch more servers.

So far, we've found that you can get away with 2 VMs per CPU, or 1 VM per 1 GHz of CPU (whichever is higher), depending on the task.

[BarBaar]

I am (trying) to run a virtualized install of Zimbra..

I have CentOS 5.1 and am using Xen (really cannot find *any* reason to run VMWare on Linux!). Anyway, hardware requirements will depend on your usage. I guess with the box you will use, you'll come a long way!

I am running +/- 10 domainU's (3 zimbra boxes) on a AMD X2 4200+ with 3 gigs ram..

But then again.. I am my only costumer. Just PoC and get experienced with the product!

[Roturgo]

Originally Posted by fcash

So far, we've found that you can get away with 2 VMs per CPU, or 1 VM per 1 GHz of CPU (whichever is higher), depending on the task.

Thanks for the info fcash! Just one question -- when you say 2 VMs per CPU, are you saying per physical CPU or per core? Would our quad-core server (dual 2.0 GHz quad-core Xeons) be capable of 16 VMs, or only 4 VMs?

[Roturgo]

Originally Posted by BarBaar

I have CentOS 5.1 and am using Xen (really cannot find *any* reason to run VMWare on Linux!).

How have you found the Xen management tools to be? We used to use Xen back in the 2.X days, but found the management tools to be lacking at best. That's mostly why we're leaning toward VMware. Has the situation improved since Xen 3 has come around?

[fcash]

Originally Posted by Roturgo

Thanks for the info fcash! Just one question -- when you say 2 VMs per CPU, are you saying per physical CPU or per core? Would our quad-core server (dual 2.0 GHz quad-core Xeons) be capable of 16 VMs, or only 4 VMs?

Per-core. A quad-core CPU should be able to handle at least 8 VMs, depending on how CPU-intensive their operation is.

[fcash]

Originally Posted by Roturgo

How have you found the Xen management tools to be? We used to use Xen back in the 2.X days, but found the management tools to be lacking at best. That's mostly why we're leaning toward VMware. Has the situation improved since Xen 3 has come around?

We've been doing things via the command-line on our current Xen 3 box, as there were no Xen management tools for Debian Linux 4.0.

xenman has been added to the Debian lenny repos, so we've been playing around with that. It's not bad, although it requires root ssh connections, and creates a new ssh connection for each command you run.

If it wasn't so expensive, and if the free version could use more than 4 GB of RAM, the enterprise versions of Xen (from Citrix) look nice.

[Roturgo]

Thanks so much for all the info fcash! It's a huge help and my team and I really appreciate it!

[windependence]

Last I looked at Xen it was difficult to install anything from CDROM as you had to mount and dismount the damn device each time. VMWare does not require this. I have also more than 2 VMs per CPU on the box I use. It's an AMD dual Opteron 2.8 GHz (single core) box with 8 gigs of RAM. I would suggest as much RAM as you can fit into the box.

-Tim

[fcash]

Never tried to install anything from CD-ROM into a Xen VM. We use the xen-tools scripts to create barebones Debian VMs via debootstrap, and then either install the needed software (for fresh VMs) or restore from backups into those VMs (for physical-to-virtual migrations).

You can have more VMs than "2 per CPU". However, we found having more than that or "1 per 1 GHz of CPU" really bogs things down. That's just a simple rule of thumb we came up with. Applies to all VMs, whether they be VServers, Jails, Zones, Xen, KVM, VirtualBox, QEmu, or VMWare.

We have one dual-Opteron box with 12 VMWare VMs installed (it's our helpdesk box with separate WinXP installs for each version of MS Office). If we run more than 4 or 5 at a time, though, things get slow. It really depends on how CPU-intensive your VMs are. If you are doing simple things like file/print/web serving, you can run plenty of VMs. If you are running things like FirstClass that use 100% of the CPU at all times, then you can only run a couple of VMs.

We came up with the "2 per CPU, or 1 per 1 GHz of CPU" maxim based on our experience with running Debian and WinXP in VMs. It's not carved in stone.