There are many things driving the need to rethink storage in today’s enterprise data center. The growth in the number of mobile devices as well as how much more information they can store and transmit over networks is increasing this need. The enterprise has yet another acronym related to this called Bring Your Own Device (BYOD). As more of us depend on having multiple devices; tablets, smart phones, laptops etc. the need to store, share synchronize information requires large, high performance storage systems to manage this data and support very high levels of concurrent access to information. In this slashdot article, I take a brief look into the specific causes and effects that mobile technology is bringing to enterprise storage.

• Why he likes storage
• His outlook on flash and the evolution of virtulization
• His expectations for Tech Field Day

Just to keep him on his toes, we finished with a pop quiz on a few ‘flash facts’. Click below to hear how he did.

Chris Evans Violin Podcast

As the Partner Business Manager for EMEA, I am involved in nearly all of our partnership discussions.  One of the first things I ask when a partner shows interest in Violin Memory is “Why do you want to sell Violin Memory?”  The answer is typically in the form of a question back to me – “What was the last revolutionary change in the storage industry?”  I’ve asked myself this question plenty of times and I realized that whatever I picked – RAID Controllers, Storage Area Networks, NAS – they all happened a long time ago in technology years.  Our partners are seeing flash storage arrays as the next revolution in the storage market and the forward looking organizations want to be in front of the crowd.

The next thing that happens in these conversations is the partner then starts to talk about the customer problems that they can solve – how accelerating applications will transform their customers’ business.  Some examples of what we are doing right now:  we are enabling a CEO to receive near real-time sales and manufacturing data so he can make more informed decisions, we are helping banks meet legal reporting requirements on time, we are deploying virtual desktops that deliver a superior user experience to standard PCs.  The experiences of real–time access to data, stress free reporting and superior virtual desktop experience were either economically or technologically unattainable before the Violin flash array.

What I have also seen is that our partners are an integral function in their customer’s IT departments.  They are able to do more than just deliver the product – they help optimize performance, trouble-shoot problems, and plan new projects.  Being a Violin partner further enhances that relationship because we enable complete service delivery by our partners.  The result is customers receive the best possible experience and fastest service.

Let us know what you think: What changes are you seeing in the partner community to help maintain a competitive advantage?

Much has been discussed about the various approaches to flash storage in the enterprise. Violin has taken an architectural path that started with early innovations in our unique Violin Switched Memory (vXM) architecture and hardware based vRAID to build a tightly integrated system that can’t be achieved with off-the-shelf components or stand-alone devices.

This design provides specific advantages in delivering a system optimized for enterprise network storage that balances performance, reliability and economics. The system approach means that all layers of the system, hardware and software, work together to deliver performance density in a high availability package. Robin Harris of StorageMojo breaks down the four layers of control in Violin Memory Arrays in a short video posted to his blog. It covers how the Flash Controller, VIMMs, vRAID, and the Array Controller all work together to maximize the performance, reliability, and efficiency of flash. Please check it out on StorageMojo.

Was it the allure of a high impact job at a hot startup, the euphoria of the “flash tornado market” or the opportunity to join an aggressive executive team with a goal to build the next storage powerhouse – based on enterprise flash storage?  I must admit it was all of the above.

Virtualization was clearly the most disruptive data center technology in the past decade.  Other advances in data center technologies have been mostly incremental, not revolutionary.   But not anymore!  Flash storage is the single biggest disruptive data center technology since the advent of virtualization.  I believe this because as the penetration and scale of virtualization in the data center increases, the current generation of storage infrastructure will crumble under the weight of massive I/O generated by virtual machines.  Data center operators are already turning to the emerging enterprise flash storage vendors to overcome the ever-increasing I/O crunch.

Violin Memory is on the forefront of this disruptive trend with its highly redundant, highly scalable all-flash networked storage system.  Watching this disruption from my seat at VMware and after doing my own personal due diligence – I decided to jump aboard the Violin Memory Express!

So, how do I feel three weeks into the job?  Seeing the v6000 series flash storage array pound out a sustained 1 million IOPS in a space-efficient 3U form factor was jaw-dropping, even for a storage bigot like me.   0 – 60mph in 2 seconds or better and it feels like I am surfing a tsunami at 100mph – a tsunami that will engulf and completely disrupt the legacy enterprise storage market as we know it today!

Narayan Venkat

Part 1 (Garbage Collection) and Part 2 (Commodity SSDs)

What about PCIe cards?

Another option is to pack as much flash as possible onto a PCIe card to sit in a high speed slot on a server.  Because of their much higher interface speeds, PCIe cards have much better performance than your typical commodity SSD, but face their own unique issues. To speak with the Operating System (OS)  PCIe cards require specialized software drivers.  With some cards these drivers are so heavy-weight that their vendors don’t even call them drivers anymore but try to convince you they are a great value added software layer. That might be true except for the fact that those cards gain their performance by stealing CPU cycles from the core that’s hosting it, the same core running the business software your trying to accelerate.  At the same time you may be paying software license fees (per core) and now have to evaluate what is serving the application vs what is needed to keep the PCIe card running.  At the same time you will require many more GB’s of DRAM to handle the metadata for the PCIe cards.

Consider the following:

• In most cases a single PCIe flash card costs 3 or 4 times that of a server itself
• Evaluate the  CPU cycles a PCIe card with a heavy driver steals from your server
• Now look at the full cost of the server and software licenses
• Then look at the cost of the PCIe card itself (in perspective)

What was the value proposition again?

To be fair, card vendors have worked to lessen their driver footprint and some have even begun to show smaller write cliffs than the commodity SSDs, but it’s still there.

So do PCie cards have a place in the data center when there are single points of failure everywhere?  Some of the higher end cards have started touting they have spare chips to swap in if they detect a failing component, some even have on-card RAID in the event of a spontaneous die failure. Such protections are of little use if the single controller managing the flash fails or crashes.

You can run multiple PCIe cards in a server but you need to choose between performance and reliability as  multiple cards typically run in a RAID-0 configurations for performance. If you wanted actual RAID data protection, you would have to use multiple cards (assuming you have enough PCIe slots) and  were willing to pay an extra ~50% (assuming 3 RAIDed cards).

Then there is the fact that a flash PCIe card is locked in a server.  You lose access to that  data  if the server crashes. So if you actually *needed* that data, then you don’t have much choice but to mirror your servers, pay a 100% overhead and taking the performance hit for mirroring. Even worse you may be paying more than 100% overhead if the card offers some on-board RAID feature that you don’t need because your already mirroring for availability reasons.

Add to this the inability to service a PCIe card in a running system and it seems clear that PCIe cards are acceptable as a memory extension technology.  Reliable cost effective data storage – probably not.   Properly deployed flash is a strategic data center resource that can’t be locked in a single server – it needs to be shared.

So the answer must be in the Storage Array’s themselves….   (part 4)

Over at Stanford they have a speaker series that has been going on for the last few… decades, called the  Stanford University Department of Electrical Engineering Computer Systems Colloquium, known to many simply as EE380. The list of past speakers is as they say, long and distinguished, and includes such industry lightweights as Joy, Lamport, Colwell, Bechtolsheim, Gray, Metcalfe, Gelsinger, Hennessy, Patterson, Brin & Page ,Diffie, Mashy, Wolfram, Cerf and Kay. For a mere mortal being invited to give an EE380 talk can be an intimidating experience, which they try to make easier by telling you that there will probably be no more than 50 people in the room, thankfully they didn’t mention that 10,000 people will watch the web cast online until after my talk was over. Yes, the other day Bennett and Rowett were added to the list of “past EE380 speakers.”

Preparation for an EE380 talk is obviously nothing to be taken lightly, but it is a fascinating opportunity because you know the audience will have an incredibly wide range of backgrounds, if you just dive straight in the deep technical stuff you will lose most of the audience who needs some introduction to the problem to give them at least some understanding of the basic issues. If you go with a “let me give you a basic over view of the subject” you will put half the room to sleep, and if you don’t get into hard data and specific details the whole room will decide you are in marketing and get up and leave.

I decided to structure the talk a little like a TV detective episode, down to the cold open, commercial break, conclusion foreshadowing, and even some “hard evidence”, i.e. we brought a few arrays for “class show and tell”. I was worried that I had made an error when early on a number of people got up from their seats, but as it turned out that was just so they could move forward to get a closer view.

Now we would like to invite you to pull your seat up and take a closer view yourself as I explain many of the key technical innovations of the Violin architecture and present hard numbers and graphs that show not only what is so right about our approach but, in ways everyone should be able to understand, what is so terribly wrong about much of what you have heard about the past, present and future of solid state storage.

Watch the VIDEO

Start From Flash

There is discussion in the industry as to the best method to deploy solid state storage, in other words whether it is better to build flash arrays from SSD’s, PCIe Cards, or the flash chips themselves. The key to system design is selecting the right building blocks and integrating them in such a way that the overall system is optimized – while minimizing tradeoffs. Violin strongly believes that you need to start from the flash layer (chips), and build an array as a coherent, tightly integrated whole to extract the extraordinary value offered by these amazingly high performance flash die.

Cost is always one of the variables that needs to be balanced in the equation. To be a price leader it’s important to be on the commodity curve. But the commodity curve can be intercepted at different levels. The Violin approach is to intercept that curve at the flash die level, not at the SSD or PCIe card level. Those devices were designed for laptops and servers, optimized as a single solitary component, not suited to storage arrays designed to provide value in the “aggregation of components” to reach some performance and/or capacity target.
 
Managing across many components requires building from the lowest level component–the flash chips–to meet the requirements that an array needs.  So much is lost in aggregating “black box” devices in which there is no chance to understand what is actually happening between the flash and the controller, it just presents a single disk interface (or PCIe if a card) and whatever performance the device can provide–due to the current state of the flash itself.
 
Violin Memory has a strategic partnership with Toshiba, one of the largest flash memory suppliers in the world. This gives Violin an inside track to create enterprise class flash controllers designed to work together as a system, not an “island of flash”. This partnership means that coupled with intelligent system design, Violin delivers the most balanced solution across the dimensions of performance, reliability, and cost. 

We want to know what you think. SSD’s are great for laptops, PCIe cards surely help servers and flash Arrays accelerate the datacenter–which would you choose for your primary storage?

Please comment below.

Related: Violin Memory Technology Series

Building from the ground up.

High end enterprises require their flash storage systems to be extremely reliable, with excellent performance density, the ability to upgrade in place, and lasting for years.

The best way to achieve that is starting the system design from scratch (the flash chips). Building from the ground up, Violin Memory is able to work with their vendors to build the best performing systems, with proven results.

It may be faster time to market to combine off the shelf SSD and/or PCIe components in an off the shelf chassis, but what often happens is the time saved is then spent with efforts to get the system to perform consistently when you don’t control the specifications of the components.

Violin Memory has a strategic partnership with Toshiba, one of the largest flash memory suppliers in the world. This affords a much greater understanding of the flash media starting at the die level. Combined with a Violin designed flash controller, and a fully integrated design, Violin Memory delivers a superior, durable product that will power datacenters for years to come.

We want to know what you think: Is 2012 the year for flash in the Enterprise?

Please comment below.

Related: Violin Memory Technology Series

Now in 2012 it seems clear that solid state storage will be the solution to balance the network-compute-storage triangle and provide the IO necessary to not only virtualize the easy applications but now tackle the hard (latency-sensitive) IO bound applications that have been fine tuned to run on dedicated servers.

The easiest way for incumbent array vendors to get in the game is to use solid state in the HDD form factor (SSD) and plug them in to the traditional storage array. Yes, you can take a Fibre Channel or SAS SSD and place them in an enterprise disk array and you will most likely see a performance increase but nowhere near the datasheet expectations of the SSD. The main issue is latency.  The big array has multiple layers of controllers (RAID, DeDup, shelf controllers, etc) to make the “array of unreliable HDD’s” appear reliable in the first place.  These layers will always reduce the “potential” offered by the SSD and in most cases only a few slots in shelf can be filled with SSDs before the shelf controller is saturated.  This obviously creates a strange looking array if you tried to fill it will all SSD’s as 80 percent of the slots would be empty because the array will be max’ed at the limits of the performance it was designed to support  At the same time the price paid for these SSD’s from the array vendor is much higher than the street prices you will find online.  It’s all about protecting those margins.

It is like buying the engine from a race car and putting it in a minivan, sure it will go faster, but not much faster, it just isn’t built to handle it.

Lets look a little deeper at why those SSD’s don’t really fit in today’s storage Array. First all of these devices use disk protocols:

• SAS (Serial Attached SCSI)
• Fibre Channel (really Fibre Channel Protocol for SCSI) SCSI
• Perhaps SATA (very slow)

Some of these newer interfaces may be faster than older disk interfaces, but they are still disk interfaces and limit the bandwidth and increase latency when used with SSDs that are capable of so much more performance.

Stepping back a bit – if you only put a handful of SSDs in a disk array they are usually used as a cache or tier.  This can be a valid strategy, but one that assumes a very good cache hit rate.  In a simple case where a single cache miss might add 10ms of latency –  it only takes a 1% miss rate to cut the performance of a single threaded application in half.

If you take a look at the specs of any enterprise storage array, it will usually have more front side bandwidth (facing the hosts) than it has backside bandwidth (facing the disks). This is a perfectly good choice for these systems since they all have large DRAM caches that serve data to users and stage writes into the disks.  The disks are rarely run at full utilization even when under high user load.  In fact, I recall being told the difference between a consumer RAID controller and an enterprise array was the consumer device had more bandwidth available to the disks than to the host while the enterprise array had more bandwidth from the cache to the users than it did to the disks. While this was probably a good design for disk systems I will show you that it’s not true for flash, and as a result the legacy disk array simply is the wrong place to put flash storage.

Remember that the reason you were considering putting SSDs in the storage array is the existing cache isn’t performing and the disks are running at full utilization. By implication this means the disks are running out of IOPs not bandwidth, so there still should be capacity for pref-etching from the SSDs, or maybe not? Remember, if the access patterns were such that IOs weren’t pre-fetchable in the first place, then you are still going to take large latency hits at the start of every access to be loaded in the SSDs. If you are lucky you will be performing large accesses to allow some amortization of the access cost, but you must be reading multiple megabytes to overcome the pre-fetch cost. And if you are reading multiple megabytes sequentially then you probably didn’t need the SSDs in the first place.

It is also likely that your SSD, like some PCIe cards, has its own internal RAID because it is possible for entire blocks to fail and on rare occasion even entire NAND die. Despite all the fancy feature names and white papers predicting ominous consequences if you don’t use a specific vendor drives with their Super Extra Special Enterprise Strength Enhanced Storage Enabled Safety Engine aka (SE)^5 ™, recovering from failed flash blocks is little different than remapping failing disk sectors which disk drives have been doing for decades. At Violin, we have a whole host of mechanisms designed to ensure every piece of data you give us is protected as one would expect from a piece of enterprise storage equipment.

But back to the beginning, the SSD has no idea if it is being used in a RAIDed array or not and must implement its own internal RAID to recover from such failures to provide the sort of data protection required for enterprise storage. So like the PCIe card, when you use the SSD in a RAIDed storage array you are paying twice for RAID.

Another issue is disks only have a limited amount of remapping space available and most arrays controllers are designed to handle a head crash in a disk where all the bad sectors are in the same place.  They aren’t designed to deal with a drive that can suddenly have thousands, or even millions bad sectors appear randomly all over a drive.  Unlike a head crash where all the bad sectors are in the same place, when a block, or worse a whole flash die fails it will contain sectors with logical block address spread over the whole address range.

Like the PCIe card is to the server, the SSD is really is just an expensive way to try boost the cache performance of an enterprise disk array and provide the incumbents an incremental introduction to the capabilities of solid state while maintain their existing profit margins and data center footprint.

If one were to take the next logical step – the flash Memory Array (Violin 3000 & 6000) is a “ground up” design to aggregate flash in most economical and reliable way to provide a path to low latency “memory speed” performance in a footprint measured in 3RU  (rack units) rather than multiple racks of short stroked hard disks.

Putting SSDs in legacy arrays is just like putting a race car engine in a minivan, the only bang you are likely to get for your buck is the sound of the under-built transmission exploding the first time you step on the gas.