Virtualisation of Servers

[bossman]

Another big thumbs up for Xenserver here, running 3 hosts (pooled) with HA for the cost of £1200 (£400 per host for the HA license) attached to Sun 7110 for VM's running 12 servers load balanced between the three.

 

I wouldn't virtualise my DC not until I had a proper system in place to bring to take them down and back up again in the proper order if ever a power cut ensued. I haven't got round to this yet but will do when I have the time and the money.

 

Installation is fairly simple just download the ISO image burn it to disk and then boot from disk and follow the instructions.

 

The SAN and 2 nics of the hosts are on a different IP range running through 2 gig switches to allow for failover the other 2 nics are load balanced and belong to the network LAN so no bandwidth issues as data just flows back and forwards from the XEN hosts to the SAN.

 

Has worked very well for over a year in fact thats how long they have been up for hehe!

 

I have not updated from version 5.6 sp2 yet to version 6 as it has a couple of issues at the moment.

 

Very happy at the moment.

[morganw]

I wouldn't virtualise my DC not until I had a proper system in place to bring to take them down and back up again in the proper order if ever a power cut ensued. I haven't got round to this yet but will do when I have the time and the money.

I have not updated from version 5.6 sp2 yet to version 6 as it has a couple of issues at the moment.

 

XenServer 6 High Availability will let you choose the restart order of VMs with an optional time delay.

[bossman]

@morganw:

 

Version 5.6 also

[morganw]

@morganw:

 

Version 5.6 also

 

I think I went from 5.6 SP1 to 6 and then found I had it, so must have been in SP2.

 

edit: ...or maybe it was FP1. It's a strange release naming convention they use.

Edited February 29, 2012 by morganw

[dhicks]

Do you actually get some kind of official Ubuntu documentation for KVM or Xen?

 

I've found the resources available for Xen (the open source version, not XenServer) running on Debian (rather than Ubuntu) to be fine. Regarding virtualising domain controllers: the issue is with people taking and then restoring snapshots of domain controllers, which confuses them somewhat. It's best to have two domain controllers in your organisation (both can be VMs) and let them replicate between themselves using their own mechanism, or use Windows backup, rather than trying to back them up using a snapshot.

[morganw]

Is that documentation generated specifically for Debian, or does the actual Xen documentation relate nicely to the versions of Xen that packaged for Debian?

[Arthur]

The KVM stuff is all free and built into Linux.

Have you ever tried KVM with ProxMox or Joyent's SmartOS? If so, are they any good?

[CyberNerd]

Have you ever tried KVM with ProxMox or Joyent's SmartOS? If so, are they any good?

Never seen it. Looks interesting, with ZFS support!

[cpjitservices]

I have tried ProxMox, it's OK but I just couldnt get into it!

 

Like I say the best option in my opinion is get CentOS, minimal install with just the Virtualization Packages. If you use CentOS 6.2 you'll get the latest versions of libvirt and virt-manager and it ..... just works now!

[CyberNerd]

I have tried ProxMox, it's OK but I just couldnt get into it!

 

Like I say the best option in my opinion is get CentOS, minimal install with just the Virtualization Packages. If you use CentOS 6.2 you'll get the latest versions of libvirt and virt-manager and it ..... just works now!

 

Out of interest, does centos include RHEV? "yum install rhev" or is it just a commercial app?

[glennda]

I tried proxmox aswell -was rather clunky and in the end i got rid. oVirt is what i'm going to look at next as mentioned above.

[Netwacky87]

Yeah - Another big thumbs up for XenServer over here, free version does exactly what we need!...I like free

[dhicks]

Is that documentation generated specifically for Debian, or does the actual Xen documentation relate nicely to the versions of Xen that packaged for Debian?

 

There's the Xen section of the Debian wiki:

 

Xen - Debian Wiki

 

This details installation of Xen on Debian, plus some troubleshooting for assorted issue, and I've found that there's generally a good selection of solutions available for Xen-onDebian when you search Google. That said, I've recently been trying to connect a PPPoE modem to a NIC passed through as a PCI device to a Xen virtual machine and have not been having having much success, and have not been able to find much documentation or discussion about it. It's worth noting that if you're buying a server for virtualisation, as well as making sure the chipset supports processor virtualisation, make sure it can support virtualisation of PCI devices too - it's a separat instruction set, for some reason, and it's bound to come in handy at some point.

[zag]

Virtualization is actually very easy.

 

Just install a new Windows 2008 R2 server with the hyper-v role. Start building new servers machines as and when you need them. You can even migrate a current server using a small utility like disk2vhd.

 

The advantages are:

 

- Quick to build new servers

- Less hardware needed

- Ability to backup/image any server in a few minutes

- Easily migrate servers to new hardware or keep copies of servers on redundant hardware

 

People who use Sans or specialist switches are taking virtualization to the extremes. You normally find that type of thing in big hosting companies or large companies. It works fine in schools but its a bit overkill imo. A simple server with a 500gb hard disk is enough for 5 or 6 virtual machines in my experience.

Edited March 1, 2012 by zag

[nicholab]

For a SAN consider dot Hill, Oracle or Dell.

 

N.B. Dot Hill were OEMing kit for HP.

[dhicks]

People who use Sans or specialist switches are taking virtualization to the extremes.

 

Agreed - specifically, SANs are useful when you want a larger amount of processing power compared to the amount of disk storage you have. In my experience, your average school (and, perhapse, other organisations, too) with an average Windows-based network wants lots of file storage space - user areas, shared areas, storage for photos, storage for videos, backups for everything, etc. Rather than spend your money on something capable of acting as a central file store, simply buy more disks to distribute around your servers.

[garethEds]

Agreed - specifically, SANs are useful when you want a larger amount of processing power compared to the amount of disk storage you have. In my experience, your average school (and, perhapse, other organisations, too) with an average Windows-based network wants lots of file storage space - user areas, shared areas, storage for photos, storage for videos, backups for everything, etc. Rather than spend your money on something capable of acting as a central file store, simply buy more disks to distribute around your servers.

 

Right - interesting, so instead of 2 x servers and a SAN what sort of hardware configurations would your recommend to someone like me who hasn't a clue but it building knowledge based on what others say? It would be nice if you could provide an example.

 

See my previous post in this thread for what we are planning - how would you change it? Please throw it out there for us to evaluate.

 

Many thanks

 

Gareth Edmondson

[CyberNerd]

Agreed - specifically, SANs are useful when you want a larger amount of processing power compared to the amount of disk storage you have. In my experience, your average school (and, perhapse, other organisations, too) with an average Windows-based network wants lots of file storage space - user areas, shared areas, storage for photos, storage for videos, backups for everything, etc. Rather than spend your money on something capable of acting as a central file store, simply buy more disks to distribute around your servers.

 

 

We probably fall into the 'large amount of processing power' bracket with our terminal servers. However SAN is extremely useful for moving data between servers! moving data between server used to take days in copying, now I just mount the LUN with the new server.

[cpjitservices]

Sorry to disappoint but the free version of oVirt is rather garbage it's VERY clunky....... almost as much as Proxmox.... Proxmox is built on Debian if I remember rightly.

[zag]

Right - interesting, so instead of 2 x servers and a SAN what sort of hardware configurations would your recommend to someone like me who hasn't a clue but it building knowledge based on what others say? It would be nice if you could provide an example.

 

See my previous post in this thread for what we are planning - how would you change it? Please throw it out there for us to evaluate.

 

Personally I would forget about the SAN and just use normal hard disks in the machines.

 

I virtualized my whole school for about 3k using standard 16gb ram dell servers. We have 3 of them running 12 Vm's on hyper-v.

 

The whole idea of going virtual is to save on resources and make things very easy to backup/migrate so the "what if the hard disk fails" argument kind of goes out the window as long as you backup properly.

 

A Backup PSU is of course a must though

 

This design doesn't stop you going with a SAN or big hardware in the future. Its easy to migrate once your machines are virtual.

[glennda]

Sorry to disappoint but the free version of oVirt is rather garbage it's VERY clunky....... almost as much as Proxmox.... Proxmox is built on Debian if I remember rightly.

 

Ah o well! I'm quite happy with Virsh to be honest and the command line! If I want a Server console i Use Xming and X11 forwarding from a windows machine

[wesleyw]

We use XenServer here (5 hosts, 2 SANs) haven't bothered with the HA as yet but DCs are virtualised (95% of servers are in fact) just the print server (seems to run quicker like that) and my TMG and proxy servers are physical just because the hosts don't have enough NIC ports to have them going through our router.

 

Wes

[dhicks]

Right - interesting, so instead of 2 x servers and a SAN what sort of hardware configurations would your recommend to someone like me who hasn't a clue but it building knowledge based on what others say?

 

Depending on how much money you have available, and whether you have two different locations to place servers:

 

One larger server - a Dell R510 (or similar from whichever supplier you prefer - VeryPC's server's look interesting, being designed to be power efficient), with as much RAM as you can reasonably afford (up to about 32GB seems to be reasonable on those at the moment, but shop around). Dual processors, with as many cores as possible, but don't worry too much about the clock speed - you want more cores available to run virtual machines. Something like the R510 will take (I think) 8 harddrives - get a good hardware RAID controller (decent ones start from about £300), but you can get harddrives from anywhere you like, Dell charge a silly amount for their harddrives. If you're using XenServer, it only uses a 4GB partition for the actual VM host OS, and I think those R510s probably have an internal USB port for a memory stick that you could use for the OS, leaving all your harddrives free for VMs.

 

For a school, you'll probably need VMs for a DC, print server, MIS, and a general apps server. If your budget only runs to the single server then you'll also need a VM for a file server. Your VM system will probably pool the storage for you and allow you to split it up at will to share between VMs as you need, but on something like Xen you can assign a VM an actual block device, so you can hand a VM a whole RAID array to itself if you want, avoiding multiple layers of abstraction at the disk layer. If you can afford a bit more, have a separate, good-sized server for file shares (just a processor, RAID card and a bunch of harddrives is all you need, so you could just build it yourself) and a big-as-you-can-afford file server for backups (but that one doesn't need to have a RAID card, it doesn't matter if it's a bit slower). Sync files nightly from your live file server to the backup with rsync or similar, deduplicating files on the backup server so you can store several weeks worth of changes to your assorted file shares.

 

If you have a separate physical location to place servers, or if you need a second server to take some load, then probably a second R510 or similar but maybe with a single processor and less RAM - just enough to run vital services if the other machine conks out and you need to get it back running. You backup server should also be able to act as a main, if slower, file server if needed.

[sjatkn]

I started our virtualisation project in a slightly unconventional way. I could not get the money to purchase a 2 hosts + SAN system so instead I went for 1 host + SAN with the 2nd host in the following years development bid. I went for a SAN so that I could use VMotion in VMWare to cope with failures in the hardware. It would be possible to do a system on the cheap by running several VM's on a single host's internal storage, but you would loose the ability to migrate them instantly on hardware failure (or maintenance).

 

Once I got the 1 host + SAN up and running I only migrated a couple of servers to it rather than everything. I did this because I did not want to get into the position of having all my critical systems running on one physical server. It did mean that I could upgrade my aging and slow SIMS server this year and then migrate other servers to the virtual environment once I get the 2nd host.

 

I did decide to get an expert in to configure VMWare and the iSCSI SAN even though I cost quite a lot. I thought that even though I could do it I wanted to make sure that the foundation of my systems were solid. The last thing I wanted with a virtual system was to have the physical systems or VMWare to be flaky. I also thought that as we are currently a little understaffed that I could not afford the time out to research and plan the setting up.

[zag]

Thats the beauty of virtualisation, you can build it in stages.

 

There is absolutely no need to do everything all in one go.