Organisations typically over provision by as much as 100% (8 of 10)

As mentioned previously organisations typically over provision by as much as 100%, so this could put a squeeze on other applications running within your infrastructure, within your internal cloud.  Therefore when providing unlimited access to resources for our critical applications and setting high priority shares, it could impact on other applications.

But what impact is that likely to have?  It may be insignificant but if it isn’t then we need to think about scaling out or up. 

Scaling out is to scale "out" to existing systems of a similar specification.  So what are the advantages of being able to do this?  One of the advantages is that you may have some existing hardware lying around which has not been deployed or provisioned or some servers that are earmarked for removal that can be added rapidly to a cluster by using the golden reference host to install ESX.

Some benefits from this approach are:

·         Short lead time. You don’t need to place an order and there is no need to wait for it to be built and delivered to you and then installed.  There’s no need for a hardware upgrade because you’ve actually put extra resources into your cluster and then DRS can migrate virtual machines to load balance. 

·         Acceptable Costs. Your costs are acceptable in this respect

·         SLA’s are met. But for how long? Are they only met for the short term?  Are there enough resources and how much more do we actually need going forward as the business grows?

Some disadvantages of this approach would be that the hardware currently available or that has been decommissioned would be older and slower than those currently out there in the market at the moment. It may not be 64 bit compatible; it may not have the latest chip technology or greater memory capacity than the latest servers do.  And while it satisfies our short term requirements, it may not meet our medium or long term objectives as the business grows and demand pressure on resources continues to grow.

You may also encounter some additional costs, such as extra software licensing based on the extra licences that you’ll need.  You may need to extend some hardware support because you have older systems and you may also find that older servers have a higher power consumption, along with having to find space to host the servers. 

Scaling Up.

So what benefits do we get from scaling upwards?  This means we scale to the latest and greatest, normally bigger and more powerful systems. Faster CPU's, more physical Memory capacity, 64bit compatible etc.  We can also look at increasing our consolidation ratio on these more powerful systems in comparison to what we currently have in place.  This helps reduce the number of systems within a data centre leading to the benefits of smaller data centres, lower power consumption, and reduce carbon footprint for example, contributing to any green IT initiatives.

These newer systems may also support hyper threading, in which the CPU scheduler within vSphere actually allows you to have more execution threads for your virtual CPU’s to execute on.

We can make efficiency savings.  After making the initial upgrade to a more powerful larger system, taking into consideration the cost of the upgrade, we may actually save over time against scaling out to older systems. It’s essential to perform a cost benefit analysis to see what savings we can make by scaling up.

Some disadvantages are:

·         Longer lead time.  You have to wait for the systems to be built and delivered / configured and installed after making an upgrade purchase. 

·         Space.  You may have to find space for your new systems and you may have to decommission some old servers within your data centre, this again extending the lead time.  The associated costs would be the cost of purchasing new equipment and any associated licensing costs that you are likely to incur by scaling upwards.

    One example of a scaling up benefit is from eBay.  A key note speech from Mazen Rawashdeeh  eBay's VP of Technology Operations at the Gartner Data centre summit in Las Vegas talked about the benefits of leasing servers.  The benefit of leasing servers is that you get a complete package for an annual fee.  By trading in your existing leased servers for the latest technology that is available on a yearly cycle.  This leads to benefits such as being greener by using more power efficient servers which uses less cO2, and reducing our physical size because we can have confidence in being able to host more VMs per ESX server and there increase the conversions of physical systems to virtual machines.

Other cost savings such as power usage, less data centre space in terms of  reducing the physical footprint, reduction in the number of software licenses, were some of the key benefits that Mazen was trying to point out why eBay had now shifted to leasing.

I’ve covered the benefits of scaling up and scaling out, but what about scaling in?

Scaling In

What is Scaling in?  Well it is the process of using the spare capacity within our infrastructure.  We previously mentioned about way of relieving the pressure on your virtual environment if experiencing capacity / performance issues.  But what about if your environment is performing as expected and you have over provisioned?

Do you have spare capacity within your infrastructure?  Consider consolidating workloads (guests) onto fewer hosts to “sweat the assets” more.  Also consider using periods of inactivity to migrate workloads between hosts.  An example would be to run batch programs overnight on hosts running working day applications.  By performing these actions you may be able to invoke the VMware Distributed Power Management (DPM) application which powers off unused hosts during these periods.  This in turn will reduce the power consumption and in turn energy costs.  It may also lead to a consolidation on the number of ESX hosts required and thus reduce the number of ESX host licenses needed.  On Friday I'll be taking a look at old habits and potential risks....

Jamie Baker
Principal Consultant