VM /ETC

Archive for the ‘replication’ Category

Recently a disgruntled vSphere administrator was able to delete 88 of his former employer’s virtual machines (VMs) remotely from a McDonald’s WiFi connection. We all know virtualization makes things a lot easier, and unfortunately, this is a scary example of the dark side of just that. I’ll argue it’s also a wake up call for IT departments to realize how virtualization changes the dynamics of data center security,  risk management, and overall data vulnerability, but I’ll leave that for the experts in those fields. What made me go “hmmmm” was the thought “what if I was on the team that had to investigate and recover from this incident?” I also wondered “What if the attack was less obvious?” What if only slight configuration changes were made to the virtual machines instead of  obvious deletions? For example adding limits and reservations to the vCPU and vRAM of the virtual guests or their resource pools thus making them sluggish, unresponsive, and unable to conduct business as usual.

How Long Would It Take To Troubleshoot And Recover?

Put yourself on the team that suddenly realized 88 VMs were gone! Where would you start? The storage  jumps out at me as a logical place to begin, but after your storage area network  is online, healthy, and normal then what? It’s time to try to crack open the VMware Black Box and scour event logs, alarms, permissions, and actions. Put that aside for a minute and think about how would you start the rebuild process and get the business reconnected!?

I don’t have an easy answer. My goal is asking you to think about this for yourself.

Warning! The Veeam Pitch

Since I work with Veeam products every day I’ll briefly suggest how they could help in this scenario. Decide for yourself what tools are best for your company. I’ll point out that Read the rest of this entry »

Figuring out whether you can replicate your VMs across your WAN to a DR site is never easy. There are many factors to consider, but luckily, one of my Veeam peers and a fellow VMware vExpert, Ricky El -Qasem has created a Replication Calculator to help figure it out.

From the post on the Virtualize Planet Blog: Replication Bandwidth Calculator | Virtualize Planet

ReplicaCalc

How many times do you get asked “how do I work out if VM Replication will work with my internet link” Well I wanted to demonstrate some way of providing a calculator without working it out in my head every time. So I made a Replication Calculation tool.  It is assumed that you provide it with 3 values:

1. Average Rate of Change.
2. The Link speed – this value should reflect the upload speed at the source site or the download speed at the target if this is less. So for example if the upload at the source is 6Mbs and 10Mbs download at the target then go for 6Mbs
3. Bandwidth % – which is the amount of bandwidth as % which achievable from the link speed specified.

Download and install ReplicaCalc from here > ReplicaCalc

Ricky describes the needed values in more detail in his post so be sure to read it all there. He also demonstrates how to use Veeam Backup and Replication to get the VM dynamic rate of change. The tool is useful whether using Veeam to replicate your VMs or not, however.

Thanks Ricky!

For more on this topic, I’ve blogged about using a bandwidth calculator to figure out whether your current WAN link is adequate or not for your replication jobs before.

Chad Sakac has a great post on his Virtual Geek blog titled The Case For And Against Stretched ESX Clusters. In this post Chad discusses the possibilities of configuring ESX Clusters between 2 different physical data centers. That is, spanning the SAN across a wide area network so that VMs can be vmotioned between sites. The concept is a frequently discussed desire of many administrators, and Chad brings to light some great points for and against this design with specific configuration details about making it work with VMware ESX.

For example, the post explores several options: Read the rest of this entry »

Avoiding storage array snapshot pitfalls in a VMware environment is an article and tip published by Scott Lowe for Searchvmware.com. Scott discusses the design challenges and implications of combining the snapshot abilities of VMware ESX with the SAN based snapshot features of storage devices. The tip points out that incorrect configuration of VMware ESX with the storage device could lead to inconsistent and unusable images when trying to recover VMs.

“Because these snapshots are not, by default, integrated in any way with VMware ESX Server, we have to perform a few extra steps to ensure consistently reliable and usable storage array snapshots.”

Read all of Scott’s tip at the link to the article above.

My “2 cents” on this is that trying to configure the combination of the two snapshots manually might not Read the rest of this entry »

Compared to VMware ESX Enterprise Edition, business continuity and high availability features are lacking when deploying Citrix XenServer “out of the box.” Specifically, XenServer does not have the built in equivalent to VI3′s HA feature. Also missing is a solution similar to VMware’s soon to be released Site Recovery Manager (SRM). However, Marathon Technologies and XenSource (now a division of Citrix) have worked together to develop everRun VM as a enterprise class answer to fault tolerant availability for Windows virtual machines hosted on Citrix XenServer. According to Marathon’s Director of Products, Michael Bilancieri, at a recent Atlanta “Virtualization for the Real World” event, the integrated solution will be generally available sometime in the 2008 Q2/Q3 time frame.

Quoting from the Best of VMworld (more on this award later in this post) white paper downloadable from the everRun link above:

Read the rest of this entry »

One of the advantages of a virtual infrastructure is the ability to cost effectively replicate your production systems to a secondary disaster recovery environment. Not only can you do this with virtual machines, but there are now several options available to allow physical servers to be replicated to a stand-by VM. This post will briefly cover several products and solutions and provide multiple commercial options and a free alternative. Read the rest of this entry »

Too many companies try to implement replication to a DR VI without upgrading the bandwidth between the primary and secondary sites. Let’s look at a simple example that can illustrate what could go wrong with inadequate bandwidth.

A company has 5 VMs that each use 20 GB virtual disks. The data is not too dynamic and data change only averages about 1o% per business day or roughly 1 GB per hr. This data change could be common activity like Active Directory replication, files saved to user home folders, application databases, and email. This is common to a small to medium sized business.

Using the Data Replication Minimum Bandwidth Requirements chart provided by NSI, makers of Double-Take, You can see that the 100 GB falls into the LAN 10Mb/s bandwidth category (in the 10% column). Click the thumbnail image to the left for a better view of the chart. We’ve already proved that this company needs better than a T1, but it’s close enough not to convince those that think their data change will be lower than 10%.

The real “gotcha” is that companies never consider how long it will take to replicate the data. Read the rest of this entry »