Glo Networks Technical Blog (Glo Blog)

In the virtualisation game VMWare are big competitors.  They’ve been selling virtual machine software since 1999 and their products are the ‘go to’ virtualisation tools for many businesses (not us at Glo). But since announcing their most recent price structure changes VMWare have experienced a huge amount of criticism from their customer base.

And we can understand why. The basic gist of the change is a cap on the RAM you can apply to your virtual machines per license. Formally licenses were required on a per processor basis alone, now, if you reach the virtual RAM cap for the number of processor’s you have licensed, you will require extra licenses to cover any additional RAM. This increase caused the change to be dubbed the ‘Memory vTax’.

When VMWare first announced this pricing change the memory allowance per license were rather low, meaning (obviously depending on the configuration of the virtual machines) some VMWare customers were looking at their licensing costs being several times what the old pricing structure would have cost. Reacting to the complaints of their customers VMWare have now raised the cap, which should keep the license costs to a more reasonable level for most customers.

Here at GloNetworks we’ve always tended towards the Microsoft Virtualization software ‘Hyper-V’ over the VMWare options, and right now we’re more confident than ever in our choice. It could be argued that WMWares virtualisation software is more ‘feature-full’ however we feel that Hyper-V’s pricing has always been more appropriate for us and our customers’ requirements. And since Microsoft have appeared to confirm they have no plans to use a similar ‘Memory Tax’ in its next Hyper-V product (Windows Server ‘8’ Hyper-V) we’re sure this will continue to be the case.

Posted by James in Applications, General, Operating Systems, Servers | 1 Comment »

As promised in “Our New Private Cloud Platform“, I’m about to divulge all our secrets. Or at least some of them. In vague deal.

I should warn you that this is a blog post aimed at technical people, who have some knowledge of Hyper-V clusters already, so if you’re looking at this from a “users” point of view you may get very lost, very fast. I’m not going to explain every little detail, because quite frankly we’d be here all day.

I feel I should start off by defining our “Private Cloud”. Cloud is term that thrown about a lot recently by marketing staff, and for that reason technical staff need to use it in front of boards and in front of the decision makers. To us techies it may be frustrating, however it’s the world we live in. If you’re uninitiated it’s a very broad term that covers:

• Infrastructure as a Service (IaaS) – Server and networking hardware, possibly server OS, such as Amazon’s AWS,
• Software as a Service (SaaS) – Software provided by a remote system, such as Google Apps (Mail, Docs, etc.), or Dropbox,
• Platform as a Service (PaaS) – Normally software infrastructure for developers to rapidly build software, such as force.com, Google’s AppEngine, or parts of Azure.

Whilst we also provide SaaS products, in this instance our small “Private Cloud” we see as an IaaS offering. It’s a small, 2 node, Hyper-V cluster that we use to run our own and customer’s systems.

As a rough outline our cluster consists of:

• 1x HP Procurve 2810-24G as our main switch,
• 1x Juniper SRX210 acts as our firewall and gateway device for some portions of our network,
• 1x IBM x3250 M3 acts as our physical Active Directory Domain Controller, and also hosts our Data Protection Manager (DPM) 2010 and System Center Virtual Machine Manager (SCVMM) virtual machine under Hyper-V,
• 2x IBM x3550 M3 act as our Hyper-V nodes,
• 1x IBM DS3512 acts as our shared storage,
• 1x QNap TS-459U+ acts as our short term backup storage,
• Several USB hard drives for off-site backup that are routinely swapped.

We’re aware that there are some issues with this design; single switch, single firewall and only 2 Hyper-V nodes. However the importance here is why we chose some of these things and why we don’t care as much right now (this was a significant investment for our small company);

1. Granted all hardware does die. In the event that a switch does we can get one on-site reasonably quickly if we needed to, however we’re yet to have a HP Procurve die on us since we’ve started business,
2. Single firewall is something that we worry about, but we’ve chosen Juniper as they are easily clustered,
3. Provided that you don’t over subscrbe 2 Hyper-V Nodes should be sufficient, however additional nodes can be introduced to the cluster easily in the future.

So whilst we are aware of the problems, I believe that we’ve engineered the system in such a manner that we’re able to introduce new hardware easily, upgrade the existing hardware, and provide some additional redundancy, including multiple switches with multi-chassis LACP links.

We’ve not built this system to compete with Amazon’s amazing AWS, however we have built it with 3 goals in mind:

1. Extensibility,
2. To use as a small reference design,
3. To virtualise our own systems more redundantly. The fact we’re able to host customer’s systems as well is a nice perk.

I won’t take you through the process of setting up your Hyper-V cluster, but I will cover a few bits and bobs that we feel a techy should be aware of before walking into a project like this, but might forget when looking at the big picture.

Clustered Shared Volume, or CSV, is the magic that makes the shared storage work. It’s a clever file system that allows multiple nodes to share the same storage. We’re yet to deploy a CSV using FC so we’re unsure if this is true for FC as well, however in the instance of both DAS and iSCSI what happens is the following;

1. The master node takes control of the storage,
2. All other nodes are notified of this, and effectively redirect all storage requests for the shared storage to the master node, over the network.

It should be clear from this that your choice of network card and switch are very important.

CSVs are not supported by Microsoft for any other use other than Hyper-V clusters. So don’t go getting any ideas.

Jumbo frames on your networking gear is a must. Generally speaking a Jumbo Frame is any ethernet frame that exceeds 1500 bytes, however they’re commonly also used as a naming convention for frames of 9000-9600 bytes (+/- 14 bytes for the header, depending on your switch(es)/NIC configuration language). If you don’t remember how IP and ethernet interact I suggest you go and refresh your memory very quickly. You should recognise the importance of having Jumbo Frames enabled very quickly; it should provide higher performance in situations where large payloads are being transmitted frequently.

At present we’re using Microsoft’s DPM 2010 to backup. The major gotcha that we didn’t see was that DPM 2010 on a Domain Controller is basically a no-no:

For a DPM server that is installed on a domain controller, only protection of data sources local to the DPM server is supported. You cannot install agents on other computers to configure protection.

SCVMM (System Center Virtual Machine Manager) 2008 R2 needs some polish. We’ve had to dive into the database once already. Don’t be afraid of it.

Other than that the project went exceedlingly smoothly. There are a few features that I wish Hyper-V had, in comparison to VMWare and Xen. And I really do wish that there were more, cheaper, graphics cards out there for RemoteFX.

However, that’s just something to plan for as a future project.

Posted by Karl in Applications, General, Hardware, Operating Systems | 2 Comments »

Since the birth of Glo Networks we’ve been virtualising servers and desktops. Those of us who worked together before Glo Networks was started have been virtualising since early 2003. It’s fair to say that we love virtualising stuff. Several of us virtualise our own home systems.

It saves you money on power, hardware and in some cases because of how Microsoft’s licensing works, we’ve actually reduced the number of licenses that some of our customers had to buy. In early 2007, we started hosting systems and services online – both ours and one of our very first customer’s. It could be said that we were at the forefront of “cloud computing”, mere weeks before the term was coined.

Recently we came to terms with the fact that our platform needed a good redesign. It had grown with us and our customers, but it was coming a bit unwieldy to maintain. Last month we put in our new solution – a small Hyper-V cluster, backed up by Microsoft’s DPM 2010, powered by IBM X Series x3550 M3′s, an IBM x3250 M3, an IBM DS3512 disk system, a QNAP TS-459+ and HP Procurve 2800 series switch.

We’re still migrating our services and customers to it, but boy does it make a difference. With all our hardware consolidated and updated we’re seeing more responsive, more manageable and more highly available systems.

Would we do anything different? Probably, but that’s the way we are at Glo Networks; always striving for something better and trying to push the limit available to us at that time.

If you’re interested we’ll be following this up with a more technical post about how we setup our cluster.

Posted by Karl in Cool Stuff, General, Servers | 1 Comment »

Recently one of our customers has been playing with Hyper V, creating virtual machines for testing purposes. We have advised them in this and have guided them through using Hyper V, and it’s features and functions. One of the questions asked by the customer was about snapshots. ‘Why not use them for backups?’ they asked.

For anyone using Hyper V, Snapshots can be a very handy tool. Allowing the swift roll back of a VM to a previous state, they were intended to be used mainly for development and testing environments. They do have their uses for production environments too however, for example; if you wished to perform a potentially risky update on software installed on a virtual machine a quick snapshot before would allow you to do so safe in the knowledge you can revert to before the update simply by loading the snapshot.

One thing that snapshots should not be used for is a substitute for backups. Although they may on the surface seem ideal for this purpose there are a few reasons this is not recommended.

• They do not provide protection against problems that may occur on the host server (the one running Hyper-V), such as a hardware problems on the physical computer or a software-related issues in the operating system.
• Programs running in the virtual machine will not be aware of the snapshot and when rolling back they will not be able to adjust correctly. For example a Exchange server on a VM which has reverted to a snapshot would expect to have connections to the same clients as it did when the snapshot was created.
• The snapshot files (.avhd) will not work, or at least not you will easily be able to revert to them, once they have been moved from their original location. This means that copying them away from the host machine (as you may if you were planning to use them as a backup) will essentially make them useless.

Please note: Our method of backing up HyperV VM’s involves the use of volume shadow copy snapshots. These are not the same as HyperV snapshots! For more info please see the following:

Hyper-v Backups on the Glo Networks Technical Blog

Hyper-V Snapshots & VSS Snapshots: the differences on the Backup Assist Blog

Hyper V Snapshots FAQ on the Technet site

Posted by James in Applications, Servers | 1 Comment »

One of our customers recently wanted to upgrade their 6 terminal server which they have hosted in a data centre, they were 5 years old and it was starting to show, with 60+ users across the 6 servers the system was starting to get slow and the costs were high for the out of date hardware they were running on. The backup of the servers was not ideal, with each of the servers backing up to each other.

Project goals –

• Upgrade the servers to new hardware
• Save money
• Better way to backup
• Faster system

We purposed to the customer that we could make their current 6 physical server in to virtual servers and host them over two powerful physical servers on a much faster connection than they currently had, back all the servers up to separate location and save them money.

The customer accepted our proposal and we recently carried out the migration over a weekend, by Monday morning the servers were all up and running as virtual server on the two new servers. The new system will save them just more than £6000 a year.

Using disk2VHD (found here) we converted the physical servers, then transferred them to the new host and set them up on Hyper-V.

As well as having backup now done to a separate space away from the host servers it also adds an extra level of disaster recovery to their system. Should they have a hardware failure, being virtual servers we can have their system up and running very quickly (less than a day) on new hardware. All users had the exact same setup as before, the only difference they noticed was that their server was much quicker.

All of this also makes future migration, upgrades or add additional servers much easier thanks to virtual servers.

Posted by Dave in General, Hardware, Operating Systems, Servers | No Comments »