Yellow Bricks

by Duncan Epping

flash

Evaluating SSDs in Virtualized Datacenters by Irfan Ahmad

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Flash-based solid-state disks (SSDs) offer impressive performance capabilities and are all the rage these days. Rightly so? Let’s find out how you can assess the performance benefit of SSDs in your own datacenter before purchasing anything and without expensive, time-consuming and usually inaccurate proofs-of-concept.

** Please note that this article is written by Irfan Ahmad, follow him on twitter and make sure to attend his webinar on the 5th of June on this topic, and vote for CloudPhysics  in the big data startup top 10. **

I was fortunate enough to have started the very first project at VMware that optimized ESX to take advantage of Flash and SSDs. Swap to Host Cache (aka Swap-to-SSD) shipped in vSphere 5. For those customers wanting to manage their DRAM spend, this feature can be a huge cost saving. It also continues to serve as a differentiator for vSphere against competitors.

Swap-to-SSD has the distinction of being the first VMware project to fully utilize the capabilities of Flash but it is certainly not the only one. Since then, every established storage vendor has entered this area, not to mention a dozen awesome startups. Some have solutions that apply broadly to all compute infrastructures, yet others have products that are specifically designed to address the hypervisor platform.

The performance capabilities of the Flash are indeed impressive. But they can cost a pretty penny. Marketing machines are in full force trying to convince you that you need a shiny hardware or software solution. An important question remains: can the actual benefit keep up with the hype? The results are mixed and worth reading through.

[Read more…] about Evaluating SSDs in Virtualized Datacenters by Irfan Ahmad

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!

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!