PowerVC has long had Software Defined Compute built atop PowerVM. In PowerVC 1.3.2, we provided a technical preview of Software Defined Networking (now part of PowerVC 1.3.3). For this release, we also decided that we would bring out a technical preview around the third piece of the trifecta – Software Defined Storage.
For our first iteration of Software Defined Storage, we were focused on a story that allowed users to have a non-SAN option for their storage. While SAN provides many benefits, not every environment necessarily has a SAN available.
In this model, we use the direct attached disks on the system and build a cluster. As hosts are added to the PowerVC system, the cluster dynamically grows, adds redundancy, optimizes, etc. Key to this is that we do it all behind the scenes. When you add a host to the PowerVC, we detect that it is “SDE ready” (more on that later) and will do all of the cluster configuration for you! After the host is added to the system, you have storage.
So, how’d we do it? A few key enablers came together:
NovaLink – Software Defined Environment Mode
The PowerVM NovaLink platform installer has a new install option called “SDE”. When you run NovaLink in this mode, the system will assign all of the I/O adapters to the NovaLink virtual machine (VM). We then use Open vSwitch for our network virtualization (this is the SDN component). The storage virtualization is also occurring through there for the tech preview.
In this mode, there is not a traditional Virtual I/O Server and no Shared Ethernet or Fibre Channel. All of the I/O virtualization is hosted through the NovaLink VM.
IBM Spectrum Scale
As you may know, IBM has a robust Software Defined Storage portfolio. One key component of this is IBM Spectrum Scale (formerly known as GPFS). PowerVC is taking advantage of the IBM Spectrum Scale component to provide its Software Define Storage tech preview.
Spectrum Scale is very powerful software, used for many different purposes. At a high level, there is a block layer and a file system. There are different backends for that block layer. Many people are familiar with the ESS solutions, but since PowerVC’s first focus is on SAN-less, we instead utilized the File Placement Optimizer (FPO) mode.
The FPO mode allows us to create a common cluster across multiple hosts using those local disks. It takes care of all the redundancy aspects – making sure that 3 copies of the data (assuming that you have 3 hosts) exist at any time.
PowerVC also takes advantage of the File System – mounting that across all of the NovaLink VMs and on the PowerVC itself. PowerVC does not contribute any storage, it just mounts the file system.
One new feature here, due to the SDE mode and Spectrum Scale, is that PowerVC’s images and disks are, in fact, just files on that Spectrum Scale file system. A virtual SCSI device is created between the virtual machine and the file.
Features / Functions
Our biggest feature is that it’s boring! Seriously.
In PowerVC, we believe in keeping things simple. Those that have worked with Spectrum Scale probably know that there are quite a few configuration options. Given that we want to configure the system in a very specific way, we didn’t think it was necessary to expose that complexity to the end administrator.
During a host registration operation, PowerVC will detect that the host is in SDE mode. If it is, the local system will be evaluated to see if it is a viable host. Things that a viable host needs:
- 2 CPU cores for the NovaLink.
- At least 4 additional disks, one of which should be a SSD.
- Should have no less than 32 GB memory on the NovaLink VM; ideally 64 GB. This helps cache the I/O calls to the system. Less memory will impact performance as you scale the number of VMs you host.
Assuming you meet these requirements, PowerVC will automatically distribute (read: copy) the Spectrum Scale installers to the NovaLink VM, install Spectrum Scale, analyze the system to determine the best configuration and then add the system to the cluster (or if the first system, create the cluster).
Once the host registration is done, you’ll find that you also have a new storage provider.
At this point, it’s just standard PowerVC! The same operations you’ve come to appreciate in PowerVC are there – deploy, capture, VM console, host maintenance mode, etc. are all available to you. Functions tied to Fibre Channel (e.g., Storage Connectivity Groups and Fibre Channel Port configuration) will ignore this new host.
You can also mix and match your existing hosts (i.e., traditional Fibre Channel/SEA) with the new software defined hosts from a single PowerVC installation.
The licensing for the tech preview requires you to have IBM Spectrum Scale licenses for use across the Power hosts. Please see the following Knowledge Center article for more information: Software-defined storage technical preview licensing
Does the idea of a PowerVM system with software defined networking, storage and compute sound appealing? If so, great!
Since this is a blog, we’ll keep the steps very high level. But for more details, refer to the PowerVC Knowledge Center for more information: Software-defined storage technical preview
The high level steps are:
- Download and Install PowerVC in the Tech Preview mode.
- Download the IBM Spectrum Scale 220.127.116.11 installers onto the PowerVC server and place them in the /opt/ibm/powervc/images/spectrum-scale/ directory.
- Install a PowerVM host in “SDE” mode.
- Register the host and deploy away!
If you follow these steps, you’ll be well on your way to trying out Software Defined Storage for PowerVM. And remember, this is a Technical Preview, and therefore is not yet supported by IBM PowerVC and must not be used in a production environment. Our intention is to get your feedback, see what features we need to add, and learn more about how to make this more useful for you!