Yellow Bricks

by Duncan Epping

virtual flash

Hybrid, flash, converged storage, what’s next? Hybrid storage stack!?

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I saw a tweet pass by from PernixData and although I already knew the world of datacenter/storage design was changing it just really sank in. Over the last 5 years we have seen the world of storage change significantly. We have seen new types of storage being introduced like all-flash-based storage, hybrid storage (mix of SSD and SATA) and hyper-converged solutions. Examples of these would be Violin Memory (all-flash), Tintri (hybrid) and Nutanix (converged). More recently object-based storage solutions are trending, as Stephen Foskett states in his article on scaling storage it is nothing new but it seems to be more relevant in this new day and age.

I would expect Frank Denneman to dive in to the whole architecture aspect as part of his “Basic elements of a flash virtualization platform” series, so I am not going in to a huge amount of depth, but I did wanted to coin this term / strategy / direction. Host based flash caching solutions like VMware vFlash (when released), PernixData, FlashSoft and others will allow you to decouple performance from capacity. It truly should be treated as a new tier of storage, an extension of your storage system! This is something which will take time to realize… as it is natural to see host based flash caching solution as an extension of your hypervisor. I have been struggling with this myself for a while to be honest. When you realize that host based flash caching is a new storage tier you will also wonder what would sit behind that new storage tier? In an existing environment it is clear what the next tier is, but in a green field deployment which components should be part of a hybrid storage stack?

Just to clarify, “hybrid” in “hybrid storage stack” refers to the usage of flash for performance requirements and spindles for capacity whereas “stack” refers to the fact that this solution is not contained with in a single box as opposed to a hybrid storage device. So the first component obviously would be host based flash caching, this would enable you to meet your performance requirements. Now, I will aim to keep things simple but there are various host based data services like replication which could be included if needed. From a capacity perspective a storage system would be needed, something that can easily scale out and is easy to manage. Object-based storage solutions are trending for a reason, and I think they could be a good fit. No need for me to explain why, when Stephen has already done that in his excellent article, lets just quote the relevant portion:

This is exactly the architecture that the latest storage arrays are adopting: Object storage inside, with loosely-coupled nodes offering truly dynamic scaling. Although many allow native API access, most of these products also include an integrated object-to-file gateway, with VMware-friendly NFS or Windows-oriented SMB as the front-end protocol. These aren’t the ideal protocols for scaly-storage access, but at least they’re compatible with existing applications.

By finally divorcing data storage from legacy RAID, these systems offer compelling advantages. Many include integrated tiering, with big, slow disks and flash storage acting in concert.

Now here comes the problem I see… These object storage solutions today are not designed to work in-conjunction with host local flash caching solutions. Not that I would expect it to cause issues from a technical perspective, but fit might cause issues from a total cost of ownership perspective. What I am saying is that many of these systems are already “optimized” for both performance and capacity. So what would be next? Smart object based storage solution that integrates with host local flash caching solutions and can easily scale out for a fair price? I haven’t seen too many (which doesn’t mean there aren’t any), it seems there is an opportunity here.

Maybe a call-to-action for all those vendors working on host based flash caching solutions… It would be nice to see reference architectures for existing environments with legacy storage, but also for green-field deployments. What if I have a brand new datacenter, where does your platform fit? How do I control cost by decoupling performance and capacity? What are good options for capacity? How well do these solutions interact / integrate? I know, a lot of questions and not a lot of answers for now… hopefully that will change.

Is flash the saviour of Software Defined Storage?

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I have this search column open on twitter with the term “software defined storage”. One thing that kept popping up in the last couple of days was a tweet from various IBM people around how SDS will change flash. Or let me quote the tweet:

“What does software-defined storage mean for the future of #flash?”

It is part of a twitter chat scheduled for today, initiated by IBM. It might be just me misreading the tweets or the IBM folks look at SDS and flash in a completely different way than I do. Yes SDS is a nice buzzword these days. I guess with the billion dollar investment in flash IBM has announced they are going all-in with regards to marketing. If you ask me they should have flipped it and the tweet should have stated: “What does flash mean for the future of Software Defined Storage?” Or to make it even sound more marketing is flash the saviour of Software Defined Storage?

Flash is a disruptive technology, and changing the way we architect our datacenters. Not only did it already allow many storage vendors to introduce additional tiers of storage it also allowed them to add an additional layer of caching in their storage devices. Some vendors even created all flash based storage systems offering thousands of IOps (some will claim millions), performance issues are a thing of the past with those devices. On top of that host local flash is the enabler of scale-out virtual storage appliances. Without flash those type of solutions would not be possible, well at least not with a decent performance.

Since a couple of years host side flash is also becoming more common. Especially since several companies jumped in to the huge gap there was and started offering caching solutions for virtualized infrastructures. These solutions allow companies who cannot move to hybrid or all-flash solutions to increase the performance of their virtual infrastructure without changing their storage platform. Basically what these solutions do is make a distinction between “data at rest” and “data in motion”. Data in motion should reside in cache, if configured properly, and data in rest should reside on your array. These solutions once again will change the way we architect our datacenters. They provide a significant performance increase removing many of the performance constraints linked to traditional storage systems; your storage system can once again focus on what it is good at… storing data / capacity / resiliency.

I think I have answered the questions, but for those who have difficulties reading between the lines, how does flash change the future of software defined storage? Flash is the enabler of many new storage devices and solutions. Be it a virtual storage appliance in a converged stack, an all-flash array, or host-side IO accelerators. Through flash new opportunities arise, new options for virtualizing existing (I/O intensive) workloads. With it many new storage solutions were developed from the ground up. Storage solutions that run on standard x86 hardware, storage solutions with tight integration with the various platforms, solutions which offer things like end-to-end QoS capabilities and a multitude of data services. These solutions can change your datacenter strategy; be a part of your software defined storage strategy to take that next step forward in optimizing your operational efficiency.

Although flash is not a must for a software defined storage strategy, I would say that it is here to stay and that it is a driving force behind many software defined storage solutions!

Introducing startup PernixData – Out of stealth!

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There are many startups out there that do something with storage these days. To be honest, many of them do the same thing and at times I wonder why on earth everyone focuses on the same segment and tries to attack it with the same product / feature set. One of the golden rules for any startup should be that you have a unique solution that will sell itself. Yes I realize that it is difficult, but if you want to succeed you will need to stand out.

About a year ago Satyam Vaghani (former VMware principal engineer who was responsible for VMFS, VAAI, VVOLs etc.) and Poojan Kumar (former VMware Data products lead and ex-Oracle Exadata founder) decided to start a company – PernixData. PernixData was conceptualized based on their experiences working on the intersection of virtualization, flash based storage and data. Today PernixData is revealed to the world. For those who don’t know, Pernix means “agile”. But what is PernixData about?

How many of you haven’t experienced storage performance problems? It probably is, in fact, the number one bottleneck in most virtualized environments. Convincing your manager (director / VP) that you need a new ultra-fast (and expensive) storage device is not easy; far from it. On top of that, data will always hit the network first before being acknowledged and every read will go over your storage network. How cool would it be if there was a seamless software solution that solves all your storage performance problems without you requiring to rip and replace your existing storage assets?

Server-side flash overcomes problems associated with network based storage and server-side caching solutions provide some respite. Yet, server-side caching solutions usually neither satisfy enterprise class requirements for availability nor transparently support clustered hypervisor features such as VMware vMotion. In addition, while they accelerate reads they fail to do much for writes. Customers are then stuck between either overhauling their entire storage infrastructure or going with caching solutions that work for limited use cases. PernixData is about to release a cool new product – a flash virtualization platform – that bridges this gap. By picking up where hypervisors left off, PernixData is planning to become the VMware of server flash and is aiming to do to server flash what VMware did to CPU and memory. So, what is this flash virtualization platform and why would you need it?

PernixData’s flash virtualization platform virtualizes all flash resources across all server nodes in a vCenter Server cluster into a single high-performance, enterprise class data tier. The great thing is that this happens in a transparent way. PernixData sits completely within the hypervisor and in the data-path of your virtual machine. Note that there are no requirements to install anything in the guest (virtual machine). PernixData is not a virtual appliance because virtual appliances introduce performance overhead and would need to be managed with all costs and complexity associated.

PernixData is also flash technology agnostic. It can leverage SSD or PCIe flash (or both) within the platform. The nice thing is that PernixData uses a scale-out architecture. As you add hosts with flash they can be dynamically added to the platform. On top of that, PernixData does both read and write acceleration while providing full data protection and is fully compatible with VM mobility solutions like vMotion, Storage vMotion, HA, DRS and Storage DRS.

Even more exciting PernixData will support both Write-through and Write-back modes. The cool part is that PernixData also ensures IO is replicated for high availability purposes. You don’t want to run your VM in Write-back mode when you cannot guaranteed data is highly available right?! I guess that is one of the unique selling points of the solution. A distributed, scale out, flash virtualization platform which is not only flash agnostic but also non-disruptive for your virtual workloads.

I would imagine this is many times cheaper than buying a new storage array. Even without knowing what the cost of PernixData will be, or which flash device (PCIe or SSD) you would decide to use… I bet when it comes to overall costs of the solution (product + implementation costs) it will be many many times cheaper.

As I started off with, the golden rule for any startup should be that they have a unique solution that sells itself. I am confident that PernixData FVP has just that by being a disruptive technology that solves a big problem in virtualized environments  in a scale-out and transparent manner while leveraging your existing storage investments.

If you want to be kept up to date, make sure to follow Satyam, Poojan , Charlie and PernixData on twitter. If you are interested in joining the PernixData FVP Beta, make sure to sign up!

Make sure to also read Frank’s article on PernixData.

<update>

I recommend watching the Storage Field Day videos for more details from Satyam Vaghani himself, note the playlist this is 4 videos!

</update>

VMworld session report: INF-STO2223 – Tech Preview vSphere Integration with Existing Storage

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A couple of weeks ago I posted an article about Virtual Volumes aka vVOLs. This week at VMworld Thomas (Tom) Phelan and Vijay Ramachandran delivered a talk which again addressed this topic but they added Virtual Flash to the mix. The session was “INF-STO2223”.

For those attending Barcelona, sign up for it! It is currently scheduled once on Wednesday at 14:00.

The session started out with a clear disclaimer, this was a technology preview and there is no guarantee whatsoever that this piece of technology will ever be released.

Tom Phelan covered Virtual Flash and Vijay covered Virtual Volumes but as Virtual Volumes was extensively covered in my other blog post I would like to refer back to that blog post for more details on that topic. This blog post will discuss the “Virtual Flash” portion of the presentation, virtual flash or vFlash in short is often also called “SSD caching”.

The whole goal of the Virtual Flash project is to allow vSphere to manage SSD as a cluster resource, just like CPU and memory today. Sounds familiar right for those who read the blog post about vCloud Distributed Storage?! The result of this project should be a framework which allows partners to insert their caching solution and utilize SSD resources more effectively without some of the current limitations.

Virtual Flash may be VM-transparent but also VM-aware. Meaning that it should for instance be possible to allocate resources per virtual machine or virtual disk. Some controls that should be included are reservations, shares and limits. On top of that, it should fully work with  vMotion and integrate with DRS.

Two concepts were explained:

  1. VM transparent caching
  2. VM-aware caching

VM transparent caching uses a hypervisor kernel caching module which sits directly in the virtual disk’s data path. It can be used in two modes, write thru cache (read only) and write back cache (read and write). On top of that it will provide the ability to migrate cache content during a vMotion or discard the cache.

VM-aware caching is a type of caching where the Virtual Flash resource is presented directly to the virtual machine as a device. This allows the virtual machine to control the caching algorithm. The cache will in this case automatically “follow” the virtual machine during migration. It should be pointed out that if the VM is powered off the cache is flushed.

For those managing virtual environments, architecting them or providing health check services… think about the most commonly faced problem, yes that typically is storage performance related. Just imagine for a second having a caching solution at your disposal which could solve most of these problems…. Indeed that would be awesome. Hopefully we will hear more soon!