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    An FAQ to Make Your Storage System Hum

    May 23rd, 2017

    In our most recent “Everything You Wanted To Know About Storage But Were Too Proud To Ask” webcast series – Part Sepia – Getting from Here to There, we discussed terms and concepts that have a profound impact on storage design and performance. If you missed the live event, I encourage you to check it our on-demand. We had many great questions on encapsulation, tunneling, IOPS, latency, jitter and quality of service (QoS). As promised, our experts have gotten together to answer them all.

    Q. Is there a way to measure jitter?

    A. Jitter can be measured directly as a statistical function of the latency, typically as the Variance or Standard Deviation of the latency. For example a storage device might show an average latency of 5ms with a standard deviation of 1.5ms. This means roughly 95% of the transactions have a latency between 2ms and 8ms (average latency plus/minus two standard deviations), however many storage customers measure jitter indirectly by showing the 99.9%, 99.99%, or 99.999% latency. For example if my storage system has 99.99% latency of 8ms, it means 99.99% of transactions have latency <=8ms and 1/10,000 of transactions have latency >8ms. Percentile latency is an indirect measure of jitter but often easier to calculate or understand than the actual jitter.

    Q. Can jitter be easily characterized for storage, media, and networks.  How and what tools are available for doing this?

    A. Jitter is usually easy to measure on a network using standard network monitoring and reporting tools. It may or may not be easy to measure on storage systems or storage media, depending on the tools available (either built-in to the storage OS or using an external management or monitoring tool).  If you can record the latency of each transaction or packet, then it’s easy to calculate and show the jitter using standard statistical measures such as Variance or Standard Deviation of the latency. What most customers do is just measure the 99.9%, 99.99%, or 99.999% latency. This is an indirect measure of jitter but is often much easier to report and understand than the actual jitter.

    Q.  Generally IOPS numbers are published for a particular block size like 8k write/read size, but in reality, IO request per second could be of mixed sizes, what is your perspective on this?

    A. Most IOPS benchmarks test only one I/O size at a time. Most individual real workloads (for example databases) also use only one I/O size.  It is true that a storage controller or HDD/SSD might need to support multiple workloads simultaneously, each with a different I/O size.  While it is possible to run benchmarks with a mix of different I/O sizes, it’s rarely done because then there are too many workload combinations to test and publish. Some storage devices do not perform well if they must handle both small random and large sequential workloads simultaneously, so a smart storage controller might assign different workload types to different disk groups.

    Q. One often misconfigured parameter is queue depth. Can you talk about how this relates to IOPS, latency and jitter?

    A. Queue depth indicates how many tasks or I/Os can be lined up for a particular controller, interface, or CPU. Having a higher queue depth ensures the CPU (or controller or interface) always has a new task to do as soon as it finishes its current task(s). This can result in higher IOPS because the CPU is less likely to have idle time between transactions. But it could also increase latency because the CPU is more likely to be multi-tasking and context switching between different tasks or workloads.

    Q. Can you please repeat all your examples of tunneling? GRE, MPLS, what others? How can it be IPv4 via IPv6?

    A. VXLAN, LISP, GRE, MPLS, IPSEC.  Any time you encapsulate and send one protocol over another and decapsulate at the other end to send the original frame that process is tunneling. In the case we showed of IPv6 over IPv4, you are taking an original IPv6 frame with its IPv6 header of source address to destination address all IPv6 and sending it over and IPv4 enabled network we are encapsulating the IPv6 frame with an IPv4 header and “tunneling” IPv6 over the IPv4 network.

    Q. I think it’d be possible to configure QoS to a point that exceeds the system capacity. Are there any safeguards on avoiding this scenario?

    A. Some types of QoS allow over-provisioning and others do not. For example a QoS that imposes only maximum limits (and no minimum guarantees) on workloads might not prevent many workloads from exceeding system capacity. If the QoS allows over-provisioning, then you should use system monitoring and alerts to warn you when system capacity has been exceeded, or when any workloads are not getting their minimum guaranteed performance.

    Q. Is there any research being done on using storage analytics along with artificial intelligence (AI) to assist with QoS?  

    A. There are a number of storage analytics products, both third party and storage vendor specific that help with QoS. Whether any of these tools may be described as using AI is debatable, since we’re in the early days of using AI to do much in the storage arena. There are many QoS research projects, and no doubt they will eventually make their way into commercially available products if they prove useful.

    Q. Are there any methods (measurements) to calculate IOPS/MBps in tier capable storage? Would it be wrong metric if we estimate based on medium level, example tier 2 (between 1 and 3)?

    A. This question needs refinement, since tiering is sometimes a cache model rather than a data movement model. And knowing the answer may not actually help! Vendors do have tools (normally internal, since they are quite complex) that can help with the planning of tiered storage.

    By now, we hope you’re not “too proud” to ask some of these storage networking questions. We’ve produced four other webcasts in this “Everything You Wanted To Know About Storage,” series to date. They are all available on-demand. And you can register here for our next one on July 6th where we’ll bring in experts to discuss:

    • Storage APIs and POSIX
    • Block, File, and Object storage
    • Byte Addressable and Logical Block Addressing
    • Log Structures and Journaling Systems

    The Ethernet Storage Forum team and I hope to see you there!



    What if Programming and Networking Had a Storage Baby? Say What?

    May 18th, 2017
    The colorful “Everything You Wanted To Know About Storage But Were Too Proud To Ask,” popular webcast series marches on! In this 6th installment, Part – Vermillion – What if Programming and Networking Had a Storage Baby, we look into some of the nitties and the gritties of storage details that are often assumed. When looking at data from the lens of an application, host, or operating system, it’s easy to forget that there are several layers of abstraction underneath each before the actual placement of data occurs. In this webcast we are going to scratch beyond the first layer to understand some of the basic taxonomies of these layers.  Continue Reading...

    SMB3 – These Questions Rock!

    April 24th, 2017
    Earlier this month, the SNIA Ethernet Storage Forum hosted a live webcast on Server Message Block (SMB), “Rockin’ and Rollin’ with SMB3.” Presenting was Ned Pyle, Microsoft SMB Program Manager. If you missed the live event, I encourage you to watch it on-demand. We had a lot of questions from the big audience this event drew, so as promised, here are answers to them all. Q. Other than that audit setup, is there a way to determine, via the OS, which SMB version is in use?  Continue Reading...

    Buffers, Queues and Caches Explained

    April 19th, 2017
    Finely tuning buffers, queues and caches can make your storage system hum. And that’s exactly what we discussed in our recent SNIA Ethernet Storage Forum webcast, ““Everything You Wanted to Know About Storage But Were Too Proud To Ask – Part Teal: The Buffering Pod.” If you missed it, it’s now available on-demand. In this blog, you’ll find detailed answers from our panel of experts to all the great questions we received during the live event. I also encourage you to check out the other on-demand webcasts in this “Too Proud To Ask” series here and stay informed on upcoming events in this series by following us on Twitter @SNIAESF.  Continue Reading...

    Storage Expert Takes on Hyperconverged Questions

    April 17th, 2017
    Last month, we were fortunate enough to have Greg Schulz, analyst and founder of Server Storage IO, as a guest speaker at our SNIA Ethernet Storage Forum webcast, “What Does Hyperconverged Mean to Storage.” If you missed it, it’s now available on-demand. Greg fielded many great questions during the live event, but we didn’t have time to get to them all. So here they are:  Continue Reading...

    Q&A on All Things iSCSI

    April 7th, 2017
    In the recent SNIA Ethernet Storage Forum iSCSI pod webcast, from our “Everything You Wanted To Know About Storage Part Were Too Proud to Ask” series, we discussed all things iSCSI. If you missed the live event, it’s now available on-demand. As promised, we’ve compiled all the webcast questions with answers from our panel of experts. If you have additional questions, please feel free to ask them in the comment field of this blog. I also encourage you to check out the other on-demand webcasts in this “Too Proud To Ask” series here and stay informed on upcoming events in this series by following us on Twitter @SNIAESF.  Continue Reading...

    Would You Like Some Rosé with Your iSCSI?

    February 3rd, 2017

    Would you like some rosé with your iSCSI? I’m guessing that no one has ever asked you that before. But we at the SNIA Ethernet Storage Forum like to get pretty colorful in our “Everything You Wanted To Know about Storage But Were Too Proud To Ask” webcast series as we group common storage terms together by color rather than by number.

    In our next live webcast, Part Rosé – The iSCSI Pod, we will focus entirely on iSCSI, one of the most used technologies in data centers today. With the increasing speeds for Ethernet, the technology is more and more appealing because of its relative low cost to implement. However, like any other storage technology, there is more here than meets the eye.

    We’ve convened a great group of experts from Cisco, Mellanox and NetApp who will start by covering the basic elements to make your life easier if you are considering using iSCSI in your architecture, diving into:

    • iSCSI definition
    • iSCSI offload
    • Host-based iSCSI
    • TCP offload

    Like nearly everything else in storage, there is more here than just a protocol. I hope you’ll register today to join us on March 2nd and learn how to make the most of your iSCSI solution. And while we won’t be able to provide the rosé wine, our panel of experts will be on-hand to answer your questions.

    We’ve Been Thinking…What Does Hyperconverged Mean to Storage?

    February 1st, 2017

    Here at the SNIA Ethernet Storage Forum (ESF), we’ve been discussing how hyperconverged adoption will impact storage. Converged Infrastructure (CI), Hyperconverged Infrastructure (HCI), along with Cluster or Cloud In a Box (CIB) are popular trend topics that have gained both industry and customer adoption. As part of data infrastructures, CI, HCI, and CIB enable simplified deployment of resources (servers, storage, I/O networking, hypervisor, application software) across different environments.

    But what do these approaches mean for the storage environment? What are the key concerns and considerations related specifically to storage? How will the storage be connected to (or included in) the platform? Who will protect and backup the data? And most importantly, how do you know that you’re asking the right questions in order to get to the right answers?

    Find out on March 15th in a live SNIA-ESF webcast, “What Does Hyperconverged Mean to Storage.” We’ve invited expert Greg Schulz, founder and analyst of Server StorageIO, to answer the questions we’ve been debating. Join us, as Greg will move beyond the hype (pun intended) to discuss:

    • What are the storage considerations for CI, CIB and HCI
    • Why fast applications and fast servers need fast I/O
    • Networking and server-storage I/O considerations
    • How to avoid aggravation-causing aggregation (bottlenecks)
    • Aggregated vs. disaggregated vs. hybrid converged
    • Planning, comparing, benchmarking and decision-making
    • Data protection, management and east-west I/O traffic
    • Application and server north-south I/O traffic

    Register today and please bring your questions. We’ll be on-hand to answer them during this event. We hope to see you there!

    Buffers, Queues, and Caches, Oh My!

    January 18th, 2017

    Buffers and Queues are part of every data center architecture, and a critical part of performance – both in improving it as well as hindering it. A well-implemented buffer can mean the difference between a finely run system and a confusing nightmare of troubleshooting. Knowing how buffers and queues work in storage can help make your storage system shine.

    However, there is something of a mystique surrounding these different data center components, as many people don’t realize just how they’re used and why. Join our team of carefully-selected experts on February 14th in the next live webcast in our “Too Proud to Ask” series, “Everything You Wanted to Know About Storage But Were Too Proud To Ask – Part Teal: The Buffering Pod” where we’ll demystify this very important aspect of data center storage. You’ll learn:

    • What are buffers, caches, and queues, and why you should care about the differences?
    • What’s the difference between a read cache and a write cache?
    • What does “queue depth” mean?
    • What’s a buffer, a ring buffer, and host memory buffer, and why does it matter?
    • What happens when things go wrong?

    These are just some of the topics we’ll be covering, and while it won’t be exhaustive look at buffers, caches and queues, you can be sure that you’ll get insight into this very important, and yet often overlooked, part of storage design.

    Register today and spend Valentine’s Day with our experts who will be on-hand to answer your questions on the spot!

    Clearing Up Confusion on Common Storage Networking Terms

    January 12th, 2017

    Do you ever feel a bit confused about common storage networking terms? You’re not alone. At our recent SNIA Ethernet Storage Forum webcast “Everything You Wanted To Know About Storage But Were Too Proud To Ask – Part Mauve,” we had experts from Cisco, Mellanox and NetApp explain the differences between:

    • Channel vs. Busses
    • Control Plane vs. Data Plane
    • Fabric vs. Network

    If you missed the live webcast, you can watch it on-demand. As promised, we’re also providing answers to the questions we got during the webcast. Between these questions and the presentation itself, we hope it will help you decode these common, but sometimes confusing terms.

    And remember, the “Everything You Wanted To Know About Storage But Were Too Proud To Ask” is a webcast series with a “colorfully-named pod” for each topic we tackle. You can register now for our next webcast: Part Teal, The Buffering Pod, on Feb. 14th.

    Q. Why do we have Fibre and Fiber

    A. Fiber Optics is the term used for the optical technology used by Fibre Channel Fabrics.  While a common story is that the “Fibre” spelling came about to accommodate the French (FC is after all, an international standard), in actuality, it was a marketing idea to create a more unique name, and in fact, it was decided to use the British spelling – “Fibre”.

    Q. Will OpenStack change all the rules of the game?

    A. Yes. OpenStack is all about centralizing the control plane of many different aspects of infrastructure.

    Q. The difference between control and data plane matters only when we discuss software defined storage and software defined networking, not in traditional switching and storage.

    A. It matters regardless. You need to understand how much each individual control plane can handle and how many control planes you have from a overall management perspective. In the case were you have too many control planes SDN and SDS can be a benefit to you.

    Q. As I’ve heard that networks use stateless protocols, would FC do the same?

    A. Fibre Channel has several different Classes, which can be either stateful or stateless. Most applications of Fibre Channel are Class 3, as it is the preferred class for SCSI traffic, A connection between Fibre Channel endpoints is always stateful (as it involves a login process to the Fibre Channel fabric). The transport protocol is augmented by Fibre Channel exchanges, which are managed on a per-hop basis. Retransmissions are handled by devices when exchanges are incomplete or lost, meaning that each exchange is a stateful transmission, but the protocol itself is considered stateless in modern SCSI-transport Fibre Channel.

    iSCSI, as a connection-oriented protocol, creates a nexus between an initiator and a target, and is considered stateful. In addition, SMB, NFSv4, ftp, and TCP are stateful protocols, while NFSv2, NFSv3, http, and IP are stateless protocols.

    Q. Where do CIFS/SMB come into the picture?

    A. CIFFS/SMB is part of a network stack.  We need to have a separate talk about network stacks and their layers.  In this presentation, we were talking primarily about the physical layer of the networks and fabrics.  To overly simplify network stacks, there are multiple layers of protocols that run on top of the physical layer.  In the case of FC, those protocols include the control plane protocols (such as FC-SW), and the data plane protocols.  In FC, the most common data plane protocol is FCP (used by SCSI, FICON, and FC-NVMe).  In the case of Ethernet, those protocols also include the control plan (such as TCP/IP), and data plane protocols.  In Ethernet, there are many commonly used data plane protocols for storage (such as iSCSI, NFS, and CIFFS/SMB)