Objective 3.2: Configure Software Defined Storage

Back again!! This time we are going to go over the relatively new VSAN. Now VMWare Virtual SAN originally came out in 5.5 U1, but has been radically overhauled for 6.0 (massive jump from VSAN 1.0 -6 J ) So what are we going to go over and have to know for the exam?

  • Configure/Manage VMware Virtual SAN
  • Create/Modify VMware Virtual Volumes (VVOLs)
  • Configure Storage Policies
  • Enable/Disable Virtual SAN Fault Domains

Now this is not going to be an exhaustive guide and information about VSAN and its use, abilities, and administration. Cormac Hogan and Rawlinson Rivera already do that so well, there is no point. I have Cormac’s Blog to the right. He has more info than you probably can process. So we will concern ourselves with a high overview of the product and the objectives.

Here comes my 50 mile high overview. VSAN is Software Defined Storage. What does this mean? While you still have physical drives and cards, you are pulling them together and creating logical containers (virtual disks) and such through software and the vmkernel. You can setup VSAN as a hybrid or all flash cluster. In the hybrid approach you have magnetic media used as the storage media and the flash is the cache. In all flash, the flash disks are used for both jobs.

When you setup the cluster, you can do it on a new cluster or you can add the feature to an existing cluster. When you do that it will take the disks and aggregate them into a single datastore available to all hosts in the VSAN cluster. You can later expand this by adding more disks or additional hosts with disks to the cluster. The cluster will run much better if all the hosts in the cluster are as close as possible to each other, just like your regular cluster. You can have machines that are just compute resources and have no local datastore or disk groups and still be able to use the VSAN datastore.

In order for a host to contribute its disks it has to have at least one SSD and one spindle disk. Those disks form what is known as a disk group. You can have more than one disk group per machine, but each one needs at least the above combination.

Virtual SAN manages the data in the form of flexible data containers called object. VSAN is known as Object Based Storage. An object is a logical volume that has its data and metadata spread distributed across the cluster. There are the following types of objects:

  • VM Home Namespace = this is where all configuration files are stored such as the .vmx, log files, vmdks and snapshot delta description files and so on.
  • VMDK = The .vmdk stores the contents of the Virtual Machine’s HD
  • VM Swap Object = This is created when the VM turns on, just like normal
  • Snapshot Delta VMDKs =Are created when snapshots are taken of the VM, each Delta is an object
  • Memory Object = Are the objects created when memory is selected as well when the snapshot is taken

Along with the objects, you have metadata that VSAN uses called a Witness. This is a component that serves as a tiebreaker when a decision needs to be made regarding the availability of surviving datastore components, after a potential failure. There may be more than one witness depending on your policy for the VM. Fortunately, this doesn’t take up much space – approximately 2MB on the old VSAN 1.0 and 4MB for version 2.0/6.0

So the part of the larger overall picture is being able to apply policies granularly. You are able to specify on a per VM basis how many copies of something you want, vs a RAID 1 where you have a blanket copy of everything regardless of its importance. SPBM (Storage Based Policy Management) allows you to define performance, and availability in the form of this policy. VSAN ensure that you have a policy for every VM. Whether it is the default or a specific one for the VM. For best results you should create and use your own, even if the requirements are the same as the default.

So those of us who used and read about VSAN 1.0 how does the new version differ? Quite a lot. This part is going to be lifted from Cormac’s Site. (Just the highlights)

  1. Scalability – Because vSphere 6.0 can now support 64 hosts in a cluster, so can VSAN
  2. Scalability – Now supports 62TB VMDK
  3. New on-disk Format (v2) – This allows a lot more components per host to be supported. It leverages VirtsoFS
  4. Support for All-Flash configuration
  5. Performance Improvement using the new Disk File System
  6. Availability improvements – You can separate racks of machines into Fault Domains
  7. New Re-Balance mechanism – rebalances components across disks, disk groups, and hosts
  8. Allowed to create your own Default VM Storage Policy
  9. Disk Evacuation granularity – You can evacuate a single disk now instead of a whole disk group
  10. Witnesses are now smarter – They can exercise more than a single vote instead of needing multiple witnesses
  11. Ability to light LEDs on disks for identification
  12. Ability to mark disks as SSD via UI
  13. VSAN supports being deployed on Routed networks
  14. Support of external disk enclosures.

As you can see this is a huge list of improvements. Now that we have a small background and explanation of the feature, let’s dig into the bullet points.

Configure/Manage VMware Virtual VSAN

So first, as mentioned before, there are a few requirements that need to be met in order for you to be able to create and configure VSAN.

  • Cache = You need one SAS or SATA SSD or PCIe Flash Device that is at least 10% of the total storage capacity. They can’t be formatted with VMFS or any other file system
  • Virtual Machine Data Storage = For Hybrid group configurations, make sure you have at least one NL-SAS, SAS, or SATA magnetic drive (sorry PATA owners). For All Flash disk groups, make sure you have at least one SAS, SATA, or PCIe Flash Device
  • Storage Controller = One SAS or SATA Host Bus Adapter that is configured in pass-through or RAID 0 mode.
  • Memory = this depends on the number of disk groups and devices that are managed by the hypervisor. Each host should contain a minimum of 32GB of RAM to accommodate for the maximum 5 disk groups and max 7 capacity devices per group
  • CPU = VSAN doesn’t take more than about 10% CPU overhead
  • If booting from SD, or USB device, the device needs to be at least 4GB
  • Hosts = You must have a minimum of 3 hosts for a cluster
  • Network = 1GB for Hybrid solutions, 10GB for all flash solutions. Multicast must be enabled on the switches – Only IPv4 is supported at this time
  • Valid License for VSAN

Now that we got all those pesky requirements out of the way. Let’s get started on actually creating the VSAN. The first thing we will need to do is create a VMkernel port for it. There is a new option for traffic as of 5.5U1 which is ….. VSAN. You can see it here:

After you are done, it will show up as being enabled you can check by looking here:

Now that is done, you will need to enable the cluster for VSAN as well. This is done under the cluster settings or when you create the cluster to begin with.

You have the option to automatically add the disks to the VSAN cluster, or if you leave in manual you will need to add the disks yourself, and new devices are not added when they are installed. After you create it you can check the status of it on the Summary page.

You can also check on the individual disks and health and configure disk groups and Fault Domains under the Manage > Settings > Virtual SAN location.

Here is a shot from my EVO:RAIL with VSAN almost fully configured

The errors are because I don’t have the VLANs fully configured for them to communicate yet. There is a lot more we could work on with VSAN but I don’t have the blog space nor the time. So moving on….

Create/Modify VMware Virtual Volumes (VVOLs)

First a quick primer on VVols. What are these things called Virtual Volumes? Why do we want them when LUNs have served us well for so long? So if you remember, one of the cool advantages of VSAN is the ability to assign policies on a per VM basis. But VSAN is limited to only certain capabilities. What if we want more? In comes VVols. Use VVols and a storage SAN that supports them, you can apply any abilities that SAN has on a per VM basis. Stealing from a VMWare blog for the definition, “VVols offer per-VM management of storage that helps deliver a software defined datacenter”. So what does this all mean? In the past you have had SANs with certain capabilities, such as deduplication, or a specific RAID type, etc. You would need to have a really good naming system or DB somewhere to list which LUN was which. However now, we have the ability for us to just set a specific set of rules for the VM in a policy and then it will find the LUN matching that set of rules for us. Pretty nifty huh?

So how do you create and modify these things now? The easiest way is to create a new datastore just like you would a regular VMFS or NFS.

  1. Select vCenter Inventory Lists > Datastores
  2. Click on the create new datastore icon
  3. Click on Placement for the datastore
  4. Click on VVol as the type

  5. Now put in the name you wish to give it, and also choose the Storage Container that is going to back it. (kind of like a LUN – you would have needed to add a Protocol Endpoint and Storage Container before getting to this point)
  6. Select the Hosts that are going to have access to it
  7. Finish

Kind of working this backwards but how do you configure them? You can do the following 4 things:

  1. Register the Storage Provider for VVols = Using VASA you configure communication between the SAN and vSphere. Without this communication nothing will work in VVols.
  2. Create a Virtual Datastore = this is to be able to create the VVol
  3. Review and Manage Endpoints = this is a logical proxy used to communicate between the virtual volumes and the virtual disks that they encapsulate. Protocol endpoints are exported along with their associated storage containers by the VASA provider.
  4. (Optional) If you host uses ISCSI-based transport to communicate with protocol endpoints representing a storage array, you can modify the default multipathing policy associated with it.

Configure Storage Policies

At the heart of all these changes is the storage policy. The storage policy is what enables all this wonderful magic to happen behind the scenes with you, the administrator, blissfully unaware. Let’s go ahead and define it as VMWare would like it defined: “A vSphere storage profile defines storage requirements for virtual machines and storage capabilities of storage providers. You use storage policies to manage the association between virtual machines and datastores.”

Where is it found? On the home page in your web client under…. Policies and Profiles. Anti-Climatic I know. Here is a picture of that when you click on it.

This gives you a list of all the profiles and polices associated with your environment. We currently are interested only in the Storage Policies so let us click on that. Depending on what products you have setup, yours might look a little different.

You can have Storage policies based off one of the following:

  • Rules based on Storage-Specific Data Services = these are based on data services that entities such as VSAN and VVols can provide, for example deduplication
  • Rules based on Tags = these are tags you, as an administrator, associate with specific datastores. You can apply more than one per datastore

Now we dig in. First thing we are going to need to do is to make sure that storage policies are enabled for the resources we want to apply them to. We do that by clicking on the Enable button underneath storage policies

When enabled you will see the next screen look like this (with your own resource names in there of course)

We can go ahead and create a storage policy now and be able to apply it to our resources. When you click on Create New VM Storage Policy, you will be presented with this screen:

Go ahead and give it a name and optionally a description. On the next screen we will define the rules that are based on our capabilities

In this one I am creating one for a Thick provisioned LUN

Unfortunately none of my datastores are compatible. You can also configure based off of tags you associate on your datastores.

Enable/Disable Virtual SAN Fault Domains

This is going to be a quick one as I am a bit tired of this post alreadyJ. In order to work with Fault Domains you will need to go to the VSAN Cluster and then click on Manage and Settings. Next on the left hand side you will see a Fault Domains. Click on it. You now have the ability to segregate hosts into specific fault domains. Click on add (+) to create a fault domain and then add the hosts to it you want. You will end up with a screen like this:

Onwards and Upwards to the next post!!