Questions[xenserver](server)

Given XenServer (7 currently) is based on CentOS, does that mean it works just like CentOS in terms of updating, CLI, administration (non-Xen specific like mdadm and boot loaders) etc?

Basically, if I want to use XenServer, then am I committing to using, learning, and working in the CentOS "way"?

We have a new (to us) server on the way and now is the time to switch hypervisors and we are set on using Xen.

Our current setup that I am familiar with and can administer efficiently is a Debian host with a couple VMs using Virtual Box which is less than ideal to say the least. Due to this, I am familiar to working in Debian and have made a conscious choice to use Debian for our servers. I administer only our servers for our small business so I do not have the diversity of other setups and other distributions to work from.

From my understanding, the way Redhat does things is a bit different from Debian based distributions and would require a learning curve of unknown amount; but a learning curve for sure.

So if I use XenServer, am I also committing to the Redhat learning curve?

I am aware that I can install Xen with a Debian based Dom0 but the consensus I have read seems to say XenServer works the best overall. However there will be a bit of configuration I will need to do such as getting our local RAID arrays up and running for the Dom0, Xen, and Network Shares, along with getting boot loaders and grub in order. I can do this configuration rather easily in Debian so I am trying to weigh the cost in time of trying to do the same configuration the CentOS way which I am afraid will add a considerable amount of time to get the new server in to Production given IT by myself for our company slowly happens in the afterhours of business; hence the question.

I am migrating a CentOS 7 system from VMware Server 2 to XenServer 6.5. The CentOS system was installed using the minimal installation. I used ovftool to convert the .vmdk file to a .img using the instructions here

https://www.mylesgray.com/virtualisation/using-vmwares-ovftool-convert-vmx-ova/

and imported this into XenServer using XenCenter. Upon booting I get the following errors:

dracut-initqueue[286]: Warning: dracut-initqueue timeout - starting timeout scripts
dracut-initqueue[286]: Warning: /dev/centos/root does not exist
dracut-initqueue[286]: Warning: /dev/centos/swap does not exist
dracut-initqueue[286]: Warning: /dev/mapper/centos-root does not exist

It goes on to start the emergency shell.

I think the problem is down to the device name of the disk. On the original system the disk is on /dev/sda. On the new system it is /dev/xvda. Using the installation disk I can boot into the rescue mode and it mounts /mnt/sysimage. I don't know how to fix the problem though. The only file I can find related to the device name is in /mnt/sysimage/boot/grub2/device.map. I tried changing this to

(hd0)    /dev/xvda

but it made no difference. I presume the logical disk manager configuration needs changing somewhere.

How can I fix this? I need simple(ish) instructions as I'm not a Linux expert, especially in relation to the boot process.

As I understand it, the only way to do a live backup of a vm in XenServer is to make a snapshot, convert the snapshot to a template, then export the template (to another server), then delete the snapshot.

What I can't find anywhere are the specs for how much space a snapshot takes, or how they work, plus I've had conflicting results from my trials so far (more on that below if anyone is interested). Are they supposed to be full copies right from the start? Or do they work on some sort of copy-on-write algorithm? Meaning they start at 0 size, and then grow over time (so if I delete them immediately after the export, I really won't need much disk space at all).

That's my question - how much free space to I need to leave on a host in order to do backups of the vm's this way?

Some more details on why I'm so confused (other than by the complete lack of documentation by Citrix on this topic):

Our issue is that space is at a premium - our disks are not huge on the hosts - only a little over 200GB each (using ssd's).

On one host, I get an error "The specified storage repository has insufficient space" when trying to take a snapshot of a 20G vm ... this host has 4 vms currently on it (100+20+20+20=160)

Yet on another host, with 2 x 100G vm's I was able to take a snapshot of one of the vm's.

I just noticed something odd in the storage tab on xencenter: Name / Type / Shared / Usage / Size / Virtual Allocation Server1 / LVM / No / 98% (205.4 GB Used) / 207.6 GB / 200.4 GB Server2 / Ext3 / No / 59% (120.9 GB Used) / 204.3 GB / 300 GB

I should note, there are no snapshots of any other vms than what I mentioned. So the first server has got 40G too much in 'virtual allocation' ... the 2nd server allowed 300 to be allocated out of the 204 available? And only saying 120 is used?

I'm looking into deploying a small (one or two host servers) non-production virtualization initiative for our company. We need it to be high performance and host shared resources for a number of users. I'm moderately familiar with both VMWare ESXi and Citrix XenServer, and know that we would be happy with either. Where I'm hitting a snag is the administration side.

From everything I'm reading, neither product currently supports any OS other than MS Windows for using their remote admin tools. Our company has been running quite happily for over a decade without deploying any Windows machines, and this does not seem like a. Good enough reason to start now. Even with some janky workaround in place to allow some degree of administration from a Linux or OS X machine, every solution I have found requires Windows for at least one component or one step in the process. I don't want to set up a Windows VM or partition just for this purpose. This would be a major expense to introduce an unwanted element into our environment, and I would very much like to avoid it.

Do I have any options for this? I'm not going to hold my breath waiting for Citrix or VMWare to get around to supporting other operating systems, so I'm pretty open to any alternatives. Do I need to roll my own solution here, and just forego the advantages of having a hypervisor OS with remote administration tools? Or is there some way of managing these systems with third-party tools that I'm not yet aware of? Any insight would be a big help.

Can anyone share their experiences (for example, this was great! This failed miserably!) with using the Hyper-V, ESXi, and XenServer virtualization platforms? Cost? Management? features? Handling load and backups and recovery?

And also minimum server requirements?

I thought Xen was a free virtualization platform for Linux. Is there a Xen and a separate XenServer platform?

Opinions and observations would be appreciated for a test rollout for our organization.