Recently Tim Hall of Oracle-Base fame wrote an article “Which Linux do you pick for Oracle Installations?” which addresses Oracle on non-virtualized Linux. Tim’s article is excellent but doesn’t take VMware virtualization into account, so without further ado, which Linux distribution should you use for Oracle virtualized on VMware?

When virtualizing Oracle with VMware, most Oracle DBAs are going to run it on some flavor of Linux. Oracle generally supports three distributions of Linux for their enterprise products: Novell’s SuSE Linux Enterprise Server (SLES), RedHat Enterprise Linux (RHEL), and Oracle Linux (OL). Each Operating System has costs, features and support implications that make it unique. You need to determine which is best for your environment. In the United States, RHEL is most popular, whereas in Europe SLES is most prevalent. Almost all of my experience is with RHEL or on downstream distributions (such as CentOS or OL) of it, but my biases shouldn’t have an impact on this evaluation. The file system for VMware’s vSphere ESX and vMA (vSphere Management Assistant) and many of the VMware appliances from EMC and PHD Virtual are RedHat/CentOS based. This shouldn’t be a deciding factor when deciding what OS for your database system, but this does come in useful in the event of the occasional esoteric troubleshooting situation.

With some minor exceptions, RHEL and OL are the same to operate — the files are almost entirely in the same location, the commands are the same, etc.

For the purpose of this evaluation, I am limiting my comparison to the latest two versions of the 64-bit x86 platform for each distribution and how they differ when run on VMware’s latest released version of vSphere (4.1U1). Partially this is being done to save me time and effort, but also these are the platforms you would decide between if you were looking to maximize database system performance.

Note: At the time of this writing, RHEL 6 and OL 6 were NOT certified for most Oracle products. This is due to the fact these versions are relatively recently released and Oracle is still certifying their products on the new versions. Also note that the VMware / SLES promotion is limited to SLES 11.

Cost:
Your main consideration here is whether you just want access to patches and updates or if you want actual support with your issues. In my nine years of running Oracle on Linux, I’ve had to open a total of two tickets on Linux support – once with RedHat, once with Oracle.

o SLES – If you’re running vSphere 4.0U2 or later and are active on qualifying VMware vSphere Software and Services SKUs, you can run an unlimited number of virtual machines and get free subscriptions to patches and updates of SLES 11 SP1. Phone and online support has varying levels and costs. You can read more about VMware’s SuSE agreement.
o OL – Oracle Linux is free to download in compiled form. If you want a subscription to patches and updates only, the cost is $119 per year per server for an unlimited number of physical CPUs. Phone and online support has varying levels and costs. You can read more about Oracle Linux in the Oracle Linux FAQ. You can also check out the Oracle Linux support pricing guide.
o RHEL – RedHat Linux can only be downloaded in compiled form with a subscription. The cheapest subscription is a Self-Support subscription which comes with a subscription to patches and updates and no other support for $349 per year per server, where each server is limited to a 2 socket configuration with 1 virtual guest. Phone and online support has varying levels and costs. You can check out the various support options and their cost on the Redhat website.

Features offered by VMware:
Do you want to use VMware features such as Paravirtualized SCSI (PVSCSI), Hot Add Memory or Hot Plug vCPUs? Do you have a specific requirement for Enhanced VMXNET Networking?

Not all the distributions and versions support all these features. For example, if your database workloads are very I/O intensive, SLES is probably not a good choice.

o SLES 10 – Networking: e1000, Enhanced VMXNET and VMXNET3 are supported. A standard install will default to e1000.
– Storage: PVSCSI is NOT supported
– Hot Add: Hot Add Memory supported, Hot Plug vCPUs NOT supported
o SLES 11 – Networking: e1000, Enhanced VMXNET and VMXNET3 are supported. A standard install will default to e1000.
– Storage: PVSCSI is NOT supported
– Hot Add: Hot Add Memory supported, Hot Plug vCPUs supported
o RHEL 5.6 – Networking: e1000, Enhanced VMXNET and VMXNET3 are supported. A standard install will default to e1000.
– Storage: PVCSCI is supported. PVSCSI is NOT supported on hard disk 1 of the virtual machines.
– Hot Add: Hot Add Memory supported, Hot Plug vCPUs NOT supported
o RHEL 6.0 – Networking: e1000, VMXNEXT3 supported. Enhanced VMXNET NOT supported. A standard install will default to VMXNET3.
– Storage: PVCSCSI is supported. A standard install will default to PVCSCI.
– Hot Add: Hot Add Memory supported, Hot Plug vCPUs supported
o OL 5.6 – Networking: e1000, Enhanced VMXNET and VMXNET3 are supported. A standard install will default to e1000.
– Storage: PVCSCI is supported. PVSCSI is NOT supported on hard disk 1 of the virtual machines.
– Hot Add: Hot Add Memory supported, Hot Plug vCPUs NOT supported
o OL 6.0 – Networking: e1000, VMXNEXT3 supported. Enhanced VMXNET NOT supported. A standard install will default to VMXNET3.
– Storage: PVCSCSI is supported. A standard install will default to PVCSCI.
– Hot Add: Hot Add Memory supported, Hot Plug vCPUs supported

Note: Previously OL 5.6 was listed in VMware’s certified list as NOT supporting Hot Add memory, but this has been changed recently.

Note: On OL, the new Unbreakable Enterprise Kernel (UEK) is NOT supported under VMware. You will have issues installing the VMware Tools if you are running this kernel.

Many companies standardize on one or two operating systems for their organization to minimize support costs. When bringing virtualization into the mix, your organization should re-evaluate your operating system choices to to get the performance and features you need.