VMware or Citrix?

Citrix released their virtualization solution named XenServer (from version 5, article XenServer is free) for free but only the time will show if it was a right decision. At first glance, it seems like a marvelous thing but there are some facts which should be investigated first. Together with XenServer, it was released central management solution XenCenter.

Let's have a look at their rival VMware (vSphere 4). XenServer is fully comparable to VMware ESX or ESXi. But what about XenCenter management? It's something more than VMware vSphere client but not so valuable as VMware vCenter Management Server. Citrix XenCenter is not the right choice in case of comparison to vCenter. The right one is Citrix Essentials but this one is not for free already. The main differences between Citrix XenCenter and Essentials are:

• XenCenter is missing alerting capabilities like send me an email when "CPU usage is too high" or when some error condition like "virtual machine power on failure" appears
• XenCenter is missing high availability support
• XenCenter is not able to show you performance data older than one day for physical or virtual servers
  

Now, let's try to propose a simple high availability (HA) solution based on Citrix/VMware products and compare their prices. Let's suppose we have 2 (3) entry level servers where each have 2 CPUs with max 6 cores per CPU (6 CPUs total). The servers are connected to a shared disk storage. The CPU speed or memory capacity is not important now. And we require HA solution to protect our virtual machines from hardware failure. Follows the analysis:

- Citrix Essentials Enterprise (1 license = 1 server):

• XenServer - 2 licenses = 0$ (3 lic = 0$)
• Essentials Enterprise - 2 lic = 5500$ (3 lic = 8250$)
• Essentials Preffered Support (optional) - 1 lic = 1500$
  
• Total cost = 7000$ or 9750$ for 3 servers
  
• Total cost without support = 5500$ or 8250$ for 3 servers

- VMware vSphere 4 Standard Edition (1 lic = 1 CPU):

• vSphere 4 Standard - 4 licenses = 3180$ (6 lic = 4770$)
• vShpere 4 Standard 1y Gold Support - 4 lic = 1092$ (6 lic = 1638$)
• vCenter 4 Foundation - 1 lic = 1495$
• vCenter 4 1y Gold Support - 1 lic = 545$
• Total cost = 6312$ or 8448$ for 3 servers
• Support is mandatory

- VMware vSphere 4 Essentials Plus Bundle (1 lic = 1 CPU)

• Licenses for 3 hosts plus vCenter Server for Essentials plus 1y Gold Support = 3624$
• Total cost = 3624$ for 2 or 3 servers
  

The prices of proposed solutions are quite different. In my opinion, the most valued solution is based on new VMware product line vSphere 4 Essentials.

There are rumors that VMware is the most expensive solution. I don't think so if I check the numbers above. Citrix's solution not covered by support is cheaper then VMware's solution with support but only for 2 servers. If I would like to add third server I would have to pay another license in case of Citrix. In case of VMware, I have still one spare license so I will use it. At first glance, XenServer seems to be free of charge but the price of added value by Citrix Essentials doesn't scale as well as in case of VMware vSphere 4 Standard Edition or vSphere 4 Essentials Plus. And what is your opinion to the topic?

VMware vSphere - OVF support

OVF or Open Virtualization Format is an open DMTF standard with intention to package and distribute virtual machines or virtual appliances among various hypervisors independently on hypervisor and CPU architecture.

VMware supports OVF format and actively participate on its development . It is supported on ESX 3.5 and VirtualCenter 2.5 but the implementation doesn't support full OVF feature set. (draft standard, version 0.9). VMware vSphere 4.0 has full native support of OVF format in version 1.0. Beside, there exists standalone VMware OVF Tool 1.0 which brings OVF support for products like VMware Workstation or VMware Server.

OVF is a packaging format for software appliances. For example, it may contain tested LAMP stack prepared for simple deployment in production. It is a way how to transport virtual machine templates portably. OVF package may contain single or more virtual machines which must be installed (deployed) before they can be run. It is not run-time virtual machine format like VMDK. Further, it provides content verification and integrity checking.

Compared to VMDK format, OVF defines complete virtual machine - virtual hardware configuration including CPU, memory, storage, networking and virtual disks. On the other hand, VMDK is in charge of virtual disks only.

Are there available any OVF packages? Yes, for example there exists OVF of VMware vCenter 2.5 for Linux or vCenter Admin Portal and many others at VMware Virtual Appliance Marketplace.

VMware vSphere - Fault Tolerance

VMware High Availability provides protection against physical servers failures running ESX hypervisors. If one host in HA cluster fails then failed virtual machines are restarted on another alive host from cluster. It ensures the host has enough resources to fulfill requirements of newly booted virtual machines. It is able to monitor virtual machine activity by checking its heartbeat as well and in case of its failure to restart it.

The next logical step is fault tolerant virtual environment. VMware vSphere 4 can do it . It provides zero downtime and data integrity of virtual machines in case of physical server failure.

When you configure a virtual machine to be fault tolerant a secondary duplicate machine is created on a different host. Then, any operation performed on the primary machine is recorded and replayed on its duplicate. If the primary fails the secondary takes over and continues running without interruption. However, current version is not able to monitor applications running inside virtual machines but it should be available in future.

VMware Fault Tolerance or VMware FT as it is denoted is cool and must have feature but to implement it means to meet these requirements:

1. VM (virtual machine) must be in HA cluster
   
2. esx host ssl certificates checking has to be enabled
   
3. VM has to be stored on shared storage
   
4. VM's virtual disks have to be in thick format, thin is not supported already
   
5. three VMkernel 1G ports are required, one for VMotion and two for FT
   
6. FT doesn't support Virtual SMP, only single processor VMs are supported!
7. physical hosts have to support hardware assisted virtualisation, no problem with recent servers

The most of requirements are common ones but points 4 and 6, for older servers 7 as well, are considerlable limitations. It's not so simple to implement VMware FT but I hope it will get better in next releases.

Finally, vSphere documentation is available at vmware.com.

RHEL 4.8 released

Yesterday, a next minor version of Red Hat Enterprise Linux 4 was released. The new version 4.8 contains the foloowing updates and enhancements:

• optimized drivers for RHEL 4 guests running on KVM hypervizor
• SAMBA update for better interoperability with Windows world
• new kernel tunables for better performance

For details, there are official release notes published at redhat.com.

VMware vSphere 4.0 editions

Yesterday, VMware uncovered new pricing and licensing model of vSphere 4.0 platform. In my opinion, VMware is trying to strictly split up the virtualization market into two parts - SMB and enterprise. I have a feeling from the table of features below that there is growing a hole between them. The competitors should catch the chance to fill it up.

• SMB editions - ESXi Single Server, Essentials and Essentials Plus
• Enterprise editions - Standard, Advanced, Enteprise and Enterprise Plus

Here is the mentioned table of features:

Linux kernel crash dumps with kdump

Kdump is official GNU/Linux kernel crash dumping mechanism. It is part of vanilla kernel. Before it, there exists some projects like LKCD for performing such things. But they weren't part of mainline kernel so you needed to patch the kernel or to rely on Linux distribution to include it. In the event of LKCD, it was difficult to configure it, especially which device to use for dumping.

The first notice about kexec (read what it is useful for and how to use it) in GNU/Linux kernel was in changelog of version 2.6.7. Kexec tool is prerequisite for kdump mechanism. Kdump was firstly mentioned in changelog of version 2.6.13.

How is it working? When the kernel crashed the new so called capture kernel is booted via kexec tool. The memory of previous crashed kernel is leaved intact and the capture kernel is able to capture it. In detail, first kernel needs to reserve some memory for capture kernel. It is used by capture kernel for booting. The consequence is the total system memory is lowered by reserverd memory size.

When the capture kernel is booted, the old memory is captured from the following virtual /proc files:

• /proc/vmcore - memory content in ELF format
  
• /proc/oldmem - really raw memory image!
  

Next, we will check how to initialize kdump mechanism, how to configure it and how to invoke it for testing purposes.

New Sun Fire servers with Xeon 5500

Sun has released a new line of servers and blade modules based on Intel Xeon 5500-series processors. The new pieces are:

• Sun Fire X2270 (1RU, 1 or 2 CPUs)
  
• Sun Fire X4170 (1RU, 1 or 2 CPUs)
  
• Sun Fire X4270 (2RU, 1 or 2 CPUs, 16 2.5" disks)
  
• Sun Fire X4275 (2RU, 1 or 2 CPUs, 12 3.5" disks)
  
• Sun Blade X6270 (1 or 2 CPUs)
  
• Sun Blade X6275 (4 CPUs)

The official announcement of new servers with additional details is published at www.sun.com.

Sun VirtualBox 2.2 released

The next version of Sun's desktop hypervisor VirtualBox was released. The new version 2.2 brings the following important changes:

• OpenGL 3D acceleration for Linux/OpenSolaris guests
• OVF appliance import/export
• USB and shared folder support for OpenSolaris
• host-only networking mode
  

More details are in official changelog.

VMware ESX and SATA controllers

VMware ESX hypervisor has supported only SCSI internal drives for a long time. The third update of ESX hypervisor introduced support for some SATA controllers like Intel ICH-7. The newest fourth update contains support of ICH-9 and ICH-10 chipsets as well. The same holds for ESXi platform.

The big difference is what SATA mode is supported. For example, the ICH-7 chipset is supported in IDE/ATA mode only, so you can't use use connected hard drives but you can access connected optical drives. The rest of the chipsets is supported in AHCI or Advanced Host Controller Interface mode. In this mode, you can access internal SATA drives.

When IDE/PATA mode is used, you will be able to see internal SATA (or emulated PATA) drives but you can't use it as VMFS storage. VMFS filesystem can be created on SCSI-based disks only.

There exists a nice knowledge base article about the topic. To better understand it, I borrowed an image from the article which is quite self-explanatory:

VMware ESX/ESXi 3.5 update 4 released

The fourth update of VMware ESX platform was released. It contains many hardware enhancements like support of new Intel Xeon 5500 procesors, SATA controllers or network interface cards. It supports new guests as well like SLES 11 released recently. The official release notes provide more comprehensive information.