|By Eric Burgener||
|November 26, 2012 07:45 AM EST||
Legacy storage architectures do not perform very efficiently in virtual computing environments. The very random, very write-intensive I/O patterns generated by virtual hosts drive storage costs up as enterprises either add spindles or look to newer storage technologies like solid state disk (SSD) to address the IOPS shortfall.
SSD costs are coming down, but they are still significantly higher than spinning disk costs. When enterprises do consider SSD, how it is used and where it is placed in the virtual infrastructure can make a big difference in how much enterprises have to spend to meet their performance requirements. It can also impose certain operational limitations that may or may not be issues in specific environments.
Some of the key considerations that need to be taken into account are SSD placement (in the host or in the SAN), high availability/failover requirements, caching vs logging architectures, and the value of preserving existing investments vs rip and replace investments that promise storage hardware specifically designed for virtual environments.
There are two basic locations to place SSD, each of which offers its own pros and cons. Host-based SSD will generally offer the lowest storage latencies, particularly if the SSD is located on PCIe cards. In non-clustered environments where it is clear that IOPS and storage latencies are the key performance problems, these types of devices can be very valuable. In most cases, they will remove storage as the performance problem.
But don't necessarily expect that in your environment, these devices will deliver their rated IOPS directly to your applications. In removing storage as the bottleneck, system performance will now be determined by whatever the next bottleneck in the system is. That could be CPU, memory, operating system, or any number of other potential issues. This phenomenon is referred to as Amdahl's Law.
What you probably care about are application IOPS. Test the devices you're considering in your environment before purchase, so you know exactly the level of performance gain they will provide to you. Then you can make a more informed decision about whether or not you can cost justify them for use with your workloads. Paying for performance you can't use is like buying a Ferrari for use on America's interstate system - you may never get out of second gear.
Raw SSD technology generally can provide blazingly fast read performance. Write performance, however, varies depending on whether you are writing randomly or sequentially. The raw technical specs on many SSD devices indicate that sequential write performance may be half that of read performance, and random write performance may be half again as slow. Write latencies may also not be deterministic because of how SSD devices manage the space they are writing to. Many SSD vendors are combining software and other infrastructure around their SSD devices to address some of these issues. If you're looking at SSD, look to the software it's packaged with to make sure the SSD capacity you're buying can be used most efficiently.
Host-based SSD introduces failover limitations. If you have implemented a product like VMware HA in your environment to automatically recover failed nodes, any data sitting in a host-based SSD device that has not been written through to shared storage will not be available on recovery. This can lead to data loss on recovery - something that may or may not be an issue in your environment. Even though SSD is non-volatile storage, if the node it is sitting in is down, you can't get to it. You can get to it after that node is recovered, but the issue here is whether or not you can automatically fail over and have access to it.
Because of this issue, most host-based SSD products implement what is called a "write-through" cache, which means that they don't acknowledge writes at SSD latencies, they actually write them through to shared disk and then send the write acknowledgement back from there. Anything on shared disk can be potentially recovered by any other node in the cluster, ensuring that no committed data is unavailable on failover. But what this means is that you won't get any write performance improvements from SSD, just better read performance.
What does your workload look like in terms of read vs write percentages? Most virtual environments are very write intensive, much more so than they ever were in physical environments, and virtual desktop infrastructure (VDI) environments can be as much as 90% writes when operating in steady state mode. If write performance is your problem, host-based SSD with a write-through cache may not help very much in the big picture.
SAN-based SSD, on the other hand, can support failover without data loss, and if implemented with a write-back cache can provide write performance speedups as well. But many implementations available for use with SAN arrays are really only designed to speed up reads. Check carefully as you consider SSD to understand how it is implemented, and how well that maps to the actual performance requirements in your environment.
Caching vs Logging Architectures
Most SSD, wherever it is implemented, is used as a cache. Sizing guidelines for caches start with the cache as a percentage of the back-end storage it is front-ending. Generally the cache needs to be somewhere between 3% to 6% of the back-end storage, so larger data store capacities require larger caches. For example, 20TB of back-end data might require 1TB of SSD cache (5%).
Caches are generally just speeding up reads, but if you are working with a write-back cache, then the cache will have to be split between SSD capacity used to speed up reads and SSD capacity used to speed up writes. Everything else being equal in terms of performance requirements, write-back caches will have to be larger than write-through caches, but will provide more balanced performance gains (across both reads and writes).
Logging architectures, by definition, speed up writes, making them a good fit for write-intensive workloads like those found in virtual computing environments. Logs provide write performance gains by taking the very random workload and essentially removing the randomness from it by writing it sequentially to a log, acknowledging the writes from there, then asynchronously de-staging them to a shared storage pool. This means that the same SSD device used in a log vs used in a cache will be faster, assuming some randomness to the workload. The write performance the guest VMs see is the performance of the log device operating in sequential write mode almost all the time, and it can result in write performance improvements of up to 10x (relative to that same device operating in the random mode it would normally be operating in). And a log provides write performance improvements for all writes from all VMs all the time. (What's also interesting is that if you are getting 10x the IOPS from your current spinning disk, given Amdahl's Law, you may not even need to purchase SSD to remove storage as the performance bottleneck.)
Logs are very small (10GB or so) and are dedicated to a host, while the shared storage pool is accessible to all nodes in a cluster and primarily handles read requests. In a 20 node cluster with 20TB of shared data, you would need 200GB for the logs (10GB x 20 hosts) vs the 1TB you would need if SSD was used as a cache. Logs are much more efficient than caches for write performance improvements, resulting in lower costs.
If logs are located on SAN-based SSD, you not only get the write performance improvements, but this design fully supports node failover without data loss, a very nice differentiator from write-through cache implementations.
But what about read performance? This is where caches excel, and a write log doesn't seem to address that. That's true, and why it's important to combine a logging architecture with storage tiering. Any SSD capacity not used by the logs can be configured into a fast tier 0, which will provide the read performance improvements for any data residing in that tier. The bottom line here is that you can get better overall storage performance improvements from a "log + tiering" design than you can from a cache design while using 50% - 90% less high performance device (in this case, SSD) capacity. In our example above, if you buy a 256GB SAN-based SSD device and use it in a 20 node cluster, you'll get SSD sequential write performance for every write all the time, and have 56GB left over to put into a tier 0. Compare that to buying 1TB+ of cache capacity at SSD prices.
With single image management technology like linked clones or other similar implementations, you can lock your VM templates into this tier, and very efficiently gain read performance improvements against the shared blocks in those templates for all child VMs all the time. Single image management technology can help make the use of SSD capacity more efficient in either a cache or a log architecture, so don't overlook it as long as it is implemented in a way that does not impinge upon your storage performance.
Purpose-Built Storage Hardware
There are some interesting new array designs that leverage SSD, sometimes in combination with some of the other technologies mentioned above (log architectures, storage tiering, single image manage-ment, spinning disk). Designed specifically with the storage performance issues in virtual environments in mind, there is no doubt that these arrays can outperform legacy arrays. But for most enterprises, that may not be the operative question.
It's rare that an enterprise doesn't already have a sizable investment in storage. Many of these existing arrays support SSD, which can be deployed in a SAN-based cache or fast tier. It's much easier, and potentially much less disruptive and expensive if existing storage investments could be leveraged to address the storage performance issues in virtual environments. It's also less risky, since most of the hot new "virtual computing-aware" arrays and appliances are built by startups, not proven vendors. If there are pure software-based options to consider that support heterogeneous storage hardware and can address the storage issues common in virtual computing environments, allowing you to potentially take advantage of SSD capacity that fits into your current arrays, this could be a simpler, more cost-effective, and less risky option than buying from a storage startup. But only, of course, if it adequately resolves your performance problem.
If there's one point you should take away from this article, it's that just blindly throwing SSD at a storage performance problem in virtual computing environments is not going to be a very efficient or cost-effective way to address your particular issues. Consider how much more performance you need, whether you need it on reads, writes, or both, whether you need to failover without data loss, and whether preserving existing storage hardware investments is important to you. SSD is a great technology, but your best value from it will come when you deploy it most efficiently.
All major researchers estimate there will be tens of billions devices - computers, smartphones, tablets, and sensors - connected to the Internet by 2020. This number will continue to grow at a rapid pace for the next several decades. With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo, November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be.
Sep. 3, 2015 10:48 AM EDT
With the Apple Watch making its way onto wrists all over the world, it’s only a matter of time before it becomes a staple in the workplace. In fact, Forrester reported that 68 percent of technology and business decision-makers characterize wearables as a top priority for 2015. Recognizing their business value early on, FinancialForce.com was the first to bring ERP to wearables, helping streamline communication across front and back office functions. In his session at @ThingsExpo, Kevin Roberts, GM of Platform at FinancialForce.com, will discuss the value of business applications on wearable ...
Sep. 3, 2015 10:45 AM EDT
SYS-CON Events announced today that Micron Technology, Inc., a global leader in advanced semiconductor systems, will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Micron’s broad portfolio of high-performance memory technologies – including DRAM, NAND and NOR Flash – is the basis for solid state drives, modules, multichip packages and other system solutions. Backed by more than 35 years of technology leadership, Micron's memory solutions enable the world's most innovative computing, consumer,...
Sep. 3, 2015 10:00 AM EDT Reads: 277
17th Cloud Expo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Meanwhile, 94% of enterprises are using some form of XaaS – software, platform, and infrastructure as a service.
Sep. 3, 2015 10:00 AM EDT Reads: 1,596
Containers are not new, but renewed commitments to performance, flexibility, and agility have propelled them to the top of the agenda today. By working without the need for virtualization and its overhead, containers are seen as the perfect way to deploy apps and services across multiple clouds. Containers can handle anything from file types to operating systems and services, including microservices. What are microservices? Unlike what the name implies, microservices are not necessarily small, but are focused on specific tasks. The ability for developers to deploy multiple containers – thous...
Sep. 3, 2015 10:00 AM EDT Reads: 107
As more intelligent IoT applications shift into gear, they’re merging into the ever-increasing traffic flow of the Internet. It won’t be long before we experience bottlenecks, as IoT traffic peaks during rush hours. Organizations that are unprepared will find themselves by the side of the road unable to cross back into the fast lane. As billions of new devices begin to communicate and exchange data – will your infrastructure be scalable enough to handle this new interconnected world?
Sep. 3, 2015 09:30 AM EDT Reads: 199
While many app developers are comfortable building apps for the smartphone, there is a whole new world out there. In his session at @ThingsExpo, Narayan Sainaney, Co-founder and CTO of Mojio, will discuss how the business case for connected car apps is growing and, with open platform companies having already done the heavy lifting, there really is no barrier to entry.
Sep. 3, 2015 09:30 AM EDT Reads: 206
SYS-CON Events announced today that the "Second Containers & Microservices Expo" will take place November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Containers and microservices have become topics of intense interest throughout the cloud developer and enterprise IT communities.
Sep. 3, 2015 09:30 AM EDT Reads: 647
Consumer IoT applications provide data about the user that just doesn’t exist in traditional PC or mobile web applications. This rich data, or “context,” enables the highly personalized consumer experiences that characterize many consumer IoT apps. This same data is also providing brands with unprecedented insight into how their connected products are being used, while, at the same time, powering highly targeted engagement and marketing opportunities. In his session at @ThingsExpo, Nathan Treloar, President and COO of Bebaio, will explore examples of brands transforming their businesses by t...
Sep. 3, 2015 09:30 AM EDT Reads: 278
WebRTC services have already permeated corporate communications in the form of videoconferencing solutions. However, WebRTC has the potential of going beyond and catalyzing a new class of services providing more than calls with capabilities such as mass-scale real-time media broadcasting, enriched and augmented video, person-to-machine and machine-to-machine communications. In his session at @ThingsExpo, Luis Lopez, CEO of Kurento, will introduce the technologies required for implementing these ideas and some early experiments performed in the Kurento open source software community in areas ...
Sep. 3, 2015 09:00 AM EDT
Akana has announced the availability of the new Akana Healthcare Solution. The API-driven solution helps healthcare organizations accelerate their transition to being secure, digitally interoperable businesses. It leverages the Health Level Seven International Fast Healthcare Interoperability Resources (HL7 FHIR) standard to enable broader business use of medical data. Akana developed the Healthcare Solution in response to healthcare businesses that want to increase electronic, multi-device access to health records while reducing operating costs and complying with government regulations.
Sep. 3, 2015 08:30 AM EDT Reads: 314
The Internet of Things is in the early stages of mainstream deployment but it promises to unlock value and rapidly transform how organizations manage, operationalize, and monetize their assets. IoT is a complex structure of hardware, sensors, applications, analytics and devices that need to be able to communicate geographically and across all functions. Once the data is collected from numerous endpoints, the challenge then becomes converting it into actionable insight.
Sep. 3, 2015 07:45 AM EDT Reads: 103
With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo in Silicon Valley. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be! Internet of @ThingsExpo, taking place Nov 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 17th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal an...
Sep. 3, 2015 05:15 AM EDT Reads: 2,022
WebRTC has had a real tough three or four years, and so have those working with it. Only a few short years ago, the development world were excited about WebRTC and proclaiming how awesome it was. You might have played with the technology a couple of years ago, only to find the extra infrastructure requirements were painful to implement and poorly documented. This probably left a bitter taste in your mouth, especially when things went wrong.
Sep. 3, 2015 05:00 AM EDT Reads: 493
The 3rd International WebRTC Summit, to be held Nov. 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA, announces that its Call for Papers is now open. Topics include all aspects of improving IT delivery by eliminating waste through automated business models leveraging cloud technologies. WebRTC Summit is co-located with 15th International Cloud Expo, 6th International Big Data Expo, 3rd International DevOps Summit and 2nd Internet of @ThingsExpo. WebRTC (Web-based Real-Time Communication) is an open source project supported by Google, Mozilla and Opera that aims to enable bro...
Sep. 3, 2015 05:00 AM EDT Reads: 1,594
Through WebRTC, audio and video communications are being embedded more easily than ever into applications, helping carriers, enterprises and independent software vendors deliver greater functionality to their end users. With today’s business world increasingly focused on outcomes, users’ growing calls for ease of use, and businesses craving smarter, tighter integration, what’s the next step in delivering a richer, more immersive experience? That richer, more fully integrated experience comes about through a Communications Platform as a Service which allows for messaging, screen sharing, video...
Sep. 3, 2015 04:00 AM EDT Reads: 735
The 17th International Cloud Expo has announced that its Call for Papers is open. 17th International Cloud Expo, to be held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, APM, APIs, Microservices, Security, Big Data, Internet of Things, DevOps and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportunity. Submit your speaking proposal today!
Sep. 3, 2015 02:30 AM EDT Reads: 1,688
In his session at @ThingsExpo, Lee Williams, a producer of the first smartphones and tablets, will talk about how he is now applying his experience in mobile technology to the design and development of the next generation of Environmental and Sustainability Services at ETwater. He will explain how M2M controllers work through wirelessly connected remote controls; and specifically delve into a retrofit option that reverse-engineers control codes of existing conventional controller systems so they don't have to be replaced and are instantly converted to become smart, connected devices.
Sep. 2, 2015 11:15 PM EDT Reads: 239
SYS-CON Events announced today that IceWarp will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. IceWarp, the leader of cloud and on-premise messaging, delivers secured email, chat, documents, conferencing and collaboration to today's mobile workforce, all in one unified interface
Sep. 2, 2015 06:00 PM EDT Reads: 471
SYS-CON Events announced today the Containers & Microservices Bootcamp, being held November 3-4, 2015, in conjunction with 17th Cloud Expo, @ThingsExpo, and @DevOpsSummit at the Santa Clara Convention Center in Santa Clara, CA. This is your chance to get started with the latest technology in the industry. Combined with real-world scenarios and use cases, the Containers and Microservices Bootcamp, led by Janakiram MSV, a Microsoft Regional Director, will include presentations as well as hands-on demos and comprehensive walkthroughs.
Sep. 2, 2015 04:45 PM EDT Reads: 405