Yellow Bricks

by Duncan Epping

vvols

Part 2: Is VSA the future of Software Defined Storage? (Customer use case)

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About 6.5 years ago I wrote this blog post around the future of Software-Defined Storage and if the VSA (virtual storage appliance) is the future for it. Last week at VMworld a customer reminded me of this article. Not because they read the article and pointed me back at it, but because they implemented what I described in this post, almost to the letter.

This customer had an interesting implementation, which kind of resembles the diagram I added to the blog post, note I added a part to the diagram which I originally left out but had mentioned in the blog (yes that is why the diagram looks like it is ancient… it is):

I want to share with you what the customer is doing because there are still plenty of customers that do not realize that this is supported. Note that this is supported by both vSAN as well as VMware Cloud Foundation, providing you a future proof, scalable, and flexible full-stack HCI architecture which does not need to be implemented in a rip and replace approach!

This customer basically leverages almost all functionality of our Software-Defined Storage offering. They have vSAN with locally attached storage devices (all NVMe) for certain workloads. They have storage arrays with vVols enabled for particular workloads. They have a VAIO Filter Driver which they use for replication. They also heavily rely on our APIs for monitoring and reporting, and as you can imagine they are a big believer in Policy-Based Management, as that is what helps them with placing workloads on a particular type of storage.

Now you may ask yourself, why on earth would they have vSAN and vVols sitting next to each other? Well, they had a significant investment in storage already, the storage solution was fully vVols capable and when they started using vSAN for certain projects they simply fell in love with Storage Policy-Based Management and decided to get it enabled for their storage systems as well. Even though the plan is to go all-in on vSAN over time, the interesting part here, in my opinion, is the “openness” of the platform. Want to go all-in on vSAN? Go ahead! Want to have traditional storage next to HCI? Go ahead! Want to use software-based data services? Go ahead! You can mix and match, and it is fully supported.

Anyway, just wanted to share that bit, and figured it would also be fun to bring up this 6.5 years old article again. One more thing, I think it is also good to realize how long these transitions tend to take. If you would have asked me in 2013 when we would see customers using this approach my guess would have been 2-3 years. Almost 6.5 years later we are starting to see this being seriously looked at. Of course, platforms have to mature, but also customers have to get comfortable with the idea. Change simply takes a lot of time.

SRM support for VVols coming!

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VMworld is coming up, which means that is “announcements season”. First announcement that I can share with you is the fact that VVols support for SRM is now officially on the roadmap. This is something Cormac and I have pushed hard for the past couple of years, and it is great to see this is finally being planned! A post about this was just published on the VMware Virtual Blocks blog and I think the following piece says it all. Read the blog for more info.

Some of our storage partners such as HP Enterprise 3PAR, HP Enterprise Nimble, and Pure Storage have developed and certified to the lastest VVol 2.0 VASA providers specification. VVol 2.0 is part of the vSphere 6.5 release and supports array-based replication with VVol.  To support VVol replication operations on these storage arrays, VMware also developed a set of PowerCLI cmdlets so common BC/DR operations such as failover, test failover, and recovery workflows can be scripted as needed. The use of PowerCLI works well for many VVol customers, but we believe many more customers will be able to take advantage of SRM orchestrated BC/DR workflows with VVol.

I can’t wait for this to be made available, and I am sure many VVol customers (and potential customers) will agree with me that this is a highly anticipated feature!

VVols design and procurement considerations

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Over the past couple of months I have had more and more discussions with customers and partners about VVols. It seems that Policy Based Management and the VVol granular capabilities are really starting to sink in, and more and more customers are starting to see the benefit of using vSphere as the management plane. The other option of course is pre-defining what is enabled on a datastore/LUN level and use spreadsheets and complex naming schemes to determine where a VM should land, far from optimal. I am not going to discuss the VVols basics at this point, if you need to know more about that simply do a search on VVol.

When having these discussions a bunch of things typically come up, these all have to do with design and procurement considerations when it comes to VVol capable storage. VMware provided a framework, and API, and based on this each vendor has developed their own implementation. These vary from vendor to vendor, as not all storage systems are created equal. So what do you have to think about when designing a VVols environment or when you are procuring new VVol capable storage? Below you find a list of questions to ask, with a short explanation of why this may be important. I will try to add new questions and considerations when I come up with them.

  • What level of software is needed for my storage system to support VVol?

In many cases, especially existing legacy storage systems, an upgrade is needed of the software to support VVols, ask:

  • What does this upgrade entail?
  • What is the risk?

When it is clear what you need to support VVols from a software point of view, ask:

  • What are the constraints and limits?
    • How many Protocol Endpoints can I have per storage system?
      • Do you support all protocols? (FC, NFS, iSCSI etc)
      • Is the IO proxied via the Protocol Endpoint? If it is, is their an impact with a large number of VMs?
        • Some systems can make a distinction between traffic type and for normal IO will not go through the PE, which means you don’t hit any PE limitations (queue depth being one)
    • How many Storage Pools can you have per storage system?
      • In some cases (legacy storage systems) the storage pool equals an existing physical construct on the array, what is it and what is the impact of this?
        • What kind of options do I select during the creation of the pool? Anything you select on a per Pool level means that when you change policy VVols may have to migrate to other pools, I prefer to avoid data movement. In some cases for instance “replication” is enabled on a storage pool level, I prefer to have this as a policy option
    • How many VVols can I have per storage system? (How many VMs do you have, and how many VVols do you expect to have per VM?)
      • In some cases, usually legacy storage systems, the number of VVols per array is limited. I have seen as “low” as 2000, with 3 VVols per VM at a mininum (typical 5) you can imagine this restricts the number of VMs you can run on single storage system

And then there is the control / management plane:

  • How is the VASA (vSphere APIs for Storage Awareness) Provider implemented?
    • There are two options here, either it comes as part of the storage system or it is provided as a virtual machine.
  • Then as part of that there’s also the decision around the availability model of the VASA Provider:
    • Is it a single instance?
    • Active/Standby?
    • Active/Active?
    • Scale-out?

Note, as it stands today, in order to power-on a VM or create a VM the VASA Provider needs to be available. Hence the availability model is probably of importance, depending on the type of environment you are designing. Also, some prefer to avoid having it implemented on the storage system, as any update means touching the storage system. Others prefer to have it as part of the storage system as it removes the need to have a separate VM that needs to be managed and maintained.

Last but not least, policy capabilities:

  • What is exposed through policy?
    • Availability? (RAID type / number of copies of object)
    •  QoS?
      • Reservations
      • Limits
    • Replication?
    • Snapshot (scheduling)?
    • Encryption?
    • Application type?
    • Thin provisioning?

I hope this helps having the conversation with your storage vendor, developing your design or guide the conversation during the procurement process. If anyone has additional considerations please leave a comment so I can add it to the list when applicable.

Virtually Speaking Podcast episode 32 – VVol 2.0

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Just wanted to share the Virtually Speaking Podcast with you, this episode (32) is on the topic of VVol 2.0 and features Pete Flecha, Ben Meadowcroft (PM for VVol) and I. Make sure to listen to it, it has some good info on where VVol is today and where it may be going in the near future!

Where do I run my VASA Vendor Provider for vVols?

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I was talking to someone before the start of the holiday season about running the Vendor Provider (VP) for vVols as a VM and what the best practices are around that. I was thinking about the implication of the VP not being available and came to the conclusion that when the VP is unavailable a bunch of things stop working out of which “bind” is probably most important.

The “bind” operation is what allows vSphere to access a given Virtual Volume (vVol), and this operation is issued during a power-on of a VM. This is how the vVols FAQ describes it:

When a vVol is created, it is not immediately accessible for IO. To Access vVol, vSphere needs to issue a “Bind” operation to a VASA Provider (VP), which creates IO access point for a vVol on a Protocol Endpoint (PE) chosen by a VP. A single PE can be the IO access point for multiple vVolss. “Unbind” Operation will remove this IO access point for a given vVol.

This means that when the VP is unavailable, you can’t power-on VMs at that particular time. For many storage systems that problem is mitigated by having the VP as part of their storage system itself, and of course there is the option to have multiple VPs as part of your solution, either in active/active or in active/standby configuration. In the case of VSAN for instance, each host has a VASA provider out of which one is active and others are standby, if the active fails the standby will take over automatically. So to be clear, it is up to the vendor to decide what type of availability to provide for the VP, some have decided to go for a single instance and rely on vSphere HA to restart the appliance, others have created active/standby etc.

But back to vVols, what if you own a storage system that requires an external VASA VP as a VM?

  • Run your VP VMs in a management cluster, if the hosts in the “production” cluster are impacted and VMs are restarted then at least the VP VMs should be up and running in your management cluster
  • Use multiple VP VMs if and when possible, if active/active or active / standby is supported make sure to run your VPs in that configuration
  • Do not use vVols for the VP itself, you don’t want to have any (circular) dependency between the availability of the VP and being able to power-on the VP itself
  • If there is no availability story for the VP, depending on the configuration of the appliance vSphere FT should be considered.

One more thing, if you are considering buying new storage, I think one question you definitely need to ask your vendor is what their story is around the VP. Is it a VM or is it part of the storage system itself? Is there an availability story for the VP, and if so is this “active/active” or “active/standby”? If not, what do they have on their roadmap around this? You are probably also asking yourself what VMware has planned to solve this problem, well there are a couple of things cooking and I can’t say too much about it. One important effort though is the inclusion of bind/unbind in the T10 SCSI standard, but as you can imagine, those things take time. (Which would allow us to power-on new VMs even when the VP is unavailable as it would be a SCSI command.) Until then, when you design a vVol environment, take the above into account when it comes to your Vendor Provider aka VP!