SSD Caching Software

Failure is Not an Option — It’s a Requirement!

I was recently reminded of a presentation made by GoDaddy way back in the 2013 Flash Memory Summit in which I first heard the statement: “Failure is not an option — it is a requirement!”  That’s certainly something that got my attention!  It just sounded wrong.

In fact, this expression was used to describe a very pragmatic approach the company’s storage team had devised to determine the exact maximum load that could be supported by any piece of its storage system.

This is key, since, at the time, GoDaddy claimed to be the world’s largest web hosting service with 11 million users, 54 million domains registered, over 5 million hosting accounts, with a 99.9% uptime guarantee (although the internal goal was 99.999% – five nines!)

The presenters outlined four stages of how validation processes had Continue reading

Intel’s Optane: Two Confusing Modes. Part 3) App Direct Mode

Exploding HeadThis post is a continuation of a four part series in The SSD Guy blog to help explain Intel’s two recently-announced modes of accessing its Optane DIMM, formally known as the “Intel Optane DC Persistent Memory.”

App Direct Mode

Intel’s App Direct Mode is the more interesting of the two Optane operating modes since it supports in-memory persistence, which opens up a new and different approach to improve the performance of tomorrow’s standard software. While today’s software operates under the assumption that data can only be persistent if it is written to slow storage (SSDs, HDDs, the cloud, etc.) Optane under App Direct Mode allows data to persist at memory speeds, as also do other nonvolatile memories like NVDIMMs under the SNIA NVM Programming Model.

App Direct Mode implements the full SNIA NVM Programming Model described in an earlier SSD Guy post and allows software to Continue reading

Intel’s Optane: Two Confusing Modes. Part 2) Memory Mode

Exploding HeadThis post is the second part of a four part series in The SSD Guy blog to help explain Intel’s two recently-announced modes of accessing its Optane DIMM, formally known as the “Intel Optane DC Persistent Memory.”

Memory Mode

The most difficult thing to understand about the Intel Optane DC Persistent Memory when used in Memory Mode is that it is not persistent.  Go back and read that again, because it didn’t make any sense the first time you read it.  It didn’t make any sense the second time either, did it?

Don’t worry.  This is not really important.  The difficulty stems from Intel’s marketing decision to call Optane DIMMs by the name “Intel Optane DC Persistent Memory.”  Had they simply called them “Optane DIMMs” like everyone expected them to then there would have been Continue reading

Intel’s Optane: Two Confusing Modes. Part 1) Overview

Exploding HeadIntel recently announced two operating modes for the company’s new Optane DIMMs, formally known as “Intel Optane DC Persistent Memory.”  The company has been trying to help the world to understand these two new operating modes but they are still pretty baffling to most of the people The SSD Guy speaks to.  Some say that the concepts make their heads want to explode!

How does Optane’s “Memory Mode” work?  How does “App Direct” Mode work?  In this four-part series will try to provide some answers.

Like all of my NVDIMM-related posts, this series challenges me with the question: “Should it be published in The SSD Guy, or in The Memory Guy?”  This is a point of endless confusion for me, since NVDIMM and Intel’s Optane blur the lines between Memory and Storage.  I have elected to post this in The SSD Guy with the hope that it will be found by readers who want to understand Optane for its storage capabilities.

Memory Mode is the easy sell for the short term.  It works with all current application software without modification.  It just makes it look like you have a TON of DRAM.

App Direct Mode is really cool if Continue reading

A New Spin on Memcache

IBM DataStore LogoData centers that use centralized storage, SANs or NAS, sometimes use servers to cache stored data and thus accelerate the average speed of storage. These caching servers sit on the network between the compute servers and storage, using a program called memcached to replicate a portion of the data stored in the data center’s centralized storage. Under this form of management more-frequently-used data presents itself faster since it has been copied into a very large DRAM in the memcached server.

Such systems have been offset over the past five or more years thanks to the growing availability of high-speed enterprise SSDs at an affordable price. Often direct-attached storage (DAS) in the form of an SSD within each server can be used to accelerate throughput. This can provide a considerable cost/performance benefit over the memcached approach since DRAM costs about 20 times as much as the flash in an SSD. Even though the DRAM chips within the memcached server run about three orders of magnitude faster than a flash SSD most of that speed is lost because the DRAM communicates over a slow LAN, so the DAS SSD’s performance is comparable to that of the memcached appliance.

There’ a catch to this approach, since the DAS SSD must be Continue reading

Comparing SSDs to Tomatoes

TomatoA few years ago The SSD Guy posted an analogy that Intel’s Jim Pappas uses to illustrate the latency differences between DRAM, an SSD, and an HDD.  If we look at DRAM latency to be a single heartbeat, then what happens when we scale that timing up to represent SSDs and HDDs?  How many heartbeats would it take to access either one, and what could you do in that time?

I still think it’s a pretty interesting way to make all these latency differences easier to understand.

Just recently I learned of a Rich Report video of a 2015 presentation in which Micron’s Ryan Baxter uses a different and equally interesting analogy based on tomatoes.

Tomatoes aren’t the first thing that comes to my mind when I think about SSDs, but this video may change my way of thinking!

The tomato slide, 9:30 into the presentation, is Continue reading

Intel Pits Optane SSDs Against NAND SSDs

Intel's Optane PyramidOnly a week after announcing its Optane Enterprise SSDs Intel has launched m.2-format Optane SSDs for end users.  It appears that we are at the onset of an Optane surge.

These SSDs communicate over the PCIe bus bringing more of the 3D XPoint’s performance to the user than would a SATA interface.

Pricing is $44 for a 16GB module and $77 for 32GB.  That’s $2.75 and $2.40 (respectively) per gigabyte, or about half the price of DRAM.  Intel says that these products will ship on April 24.

What’s most interesting about Intel’s Optane pitch is that the company appears to be telling the world that SSDs are no longer important with its use of the slogan: “Get the speed, keep the capacity.” This message is designed to directly address the quandary that faces PC buyers when considering an SSD: Do they want an SSD’s speed so much that they are willing to accept either Continue reading

IBM Refreshes Broad Swath of Flash Offerings

IBM Storwize All FlashYesterday IBM unveiled a sweeping update of its existing flash storage products.  These updates cover a range of products, including IBM Storwize All Flash arrays: V7000F, V7000 Gen2+, and V5030F, the FlashSystem V9000, the IBM SAN Volume Controller (SVC), and IBM’s Spectrum Virtualize Software.

The company referred to this effort as a part of a: “Drumbeat of flash storage announcements.”  IBM has a stated goal of providing its clients with: “The right flash for the right performance at the right price.”

IBM’s representatives explained that the updates were made possible by the fact that the prices of flash components have been dropping at a rapid pace while reliability is on the rise.  The SSD Guy couldn’t agree more.

Here’s what IBM announced:

Starting from the low end and moving up, the V5030F entry-level/midrange array is an Continue reading

Baidu Goes Beyond SSDs

Baidu's SDF: Software-Defined FlashI have to admit that it’s embarrassing when The SSD Guy misses something important in the world of flash storage, but I only recently learned of a paper that Baidu, China’s leading search engine, presented at the ASPLOS conference a year ago.  The paper details how Baidu changed the way they use flash to gain significant benefits over their original SSD-based systems.

After having deployed 300,000 standard SSDs over the preceding seven years, Baidu engineers looked for ways to achieve higher performance and more efficient use of the flash they were buying.  Their approach was to strip the SSD of all functions that could be better performed by the host server, and to reconfigure the application software and operating system to make the best of flash’s idiosyncrasies.

You can only  do this if you have control of both the system hardware and software.

The result was SDF, or “Software-Defined Flash”, a card that Continue reading

IBM Adds Server-Side Caching

IBM's FlashCache Server-Side Caching SoftwareIBM today announced its FlashCache Storage Accelerator, a software product that supports flash caching in a broad range of systems.  FlashCache operates over three families of IBM servers (System x, BladeCenter and Flex System) and a variety of flash types to accelerate any back-end storage, including non-IBM storage arrays.

Although the cache’s data is dynamically updated to match the random workloads of virtualized systems (i.e. to accelerate VMware), it also improves the performance of Windows and Linux environments.

The cache uses a Write Through policy to solve a number of Continue reading