Xen masters take aim at VMware
Virtual Iron and XenSource offerings lack power and polish of the virtualization leader, but they're gaining fastFollow @pvenezia
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Building VMs on XenEnterprise is simple but requires specific OS templates be present on the server itself for non-Windows VMs. When the Linux pack is installed, templates are presented for most major distributions from Red Hat and Suse, as well as for Debian Sarge. These templates are necessary because XenEnterprise relies on paravirtualization to run these VMs: They don't truly run in their own emulated server space. Windows guests are handled differently: It's possible to boot a Windows VM from a Windows Server 2003 install CD and build the VM from scratch.
Tripped up again
My first VM installation on XenEnterprise flushed out a few problems. I initially configured a new Red Hat Enterprise Linux 4 Update 4 VM with 1GB of RAM and an 8GB disk. Once I started the new VM and linked to the console, XenEnterprise's customized Red Hat Enterprise Linux 4 installer was already running. I ran through the familiar installer, opting to do the installation via NFS. When configuring the NFS mount to find the required installation packages, I inadvertently mapped to an NFS directory containing the x86_64 version of Red Hat Enterprise Linux 4 Update 4, not the i386 version. Rather than throwing an error, the management application and the server itself locked up tight, requiring a reboot. After that, I was able to build Red Hat Enterprise Linux 4 Update 4 and Windows Server 2003 VMs with no issues, as long as I was sure not to use 64-bit versions.
XenEnterprise doesn't claim to support 64-bit VMs, so the fact that they didn't run on the server wasn't a surprise. But the server locking up certainly was -- a warning dialog here is really mandatory.
Once I had several VMs running on the server, I brought the iSCSI SAN into the fray. I quickly discovered that there's no way to do this via the management application, as all disk management occurs at the command line. I'm no stranger to the open-iSCSI toolset, so I quickly configured the server to map a LUN from the NetApp StoreVault and presented it to the OS as a new device. That's when things got a little interesting. After some research on XenSource's forums, I found the back-end commands required to present that volume to the Xen service and rebooted the server. Much to my surprise, my local disk store was replaced with the new disk store, leaving my VMs without any disk. However, I could create new VMs with their virtual disks residing on the SAN array. Suffice it to say that this basic iSCSI support will be fine for those well versed in Linux and iSCSI, but largely insurmountable for those without this experience.