Welcome!

AJAX & REA Authors: Liz McMillan, Elizabeth White, David H Deans, Pat Romanski, Scott Hirsch

Related Topics: Big Data Journal, Java, Open Source, Virtualization, Red Hat, Cloud Expo

Big Data Journal: Blog Feed Post

Big Data – Storage Mediums and Data Structures

Big Data presents something of a storage dilemma. There is no one data store to rule them all.

My working title was Big Data, Storage Dilemma.

They say dilemma. I say dilemna. I'm serious. I spell it dilemna.

Big Data presents something of a storage dilemma. There is no one data store to rule them all.

Should different data structures be persisted to different storage mediums?

Storage Medium
Identifying the appropriate medium is a function of performance, cost, and capacity.

Random Access Memory
It's fast. Very. It's expense. Very.

If we are configuring an HP DL980 G7 server, it will cost $3,672 for 128GB of memory with 8x 16GB modules or $9,996 for 128GB of memory with 4x 32GB modules. That is $28-78 / GB.

We can configure an HP DL980 G7 server with up to 4TB of memory.

Solid State Drive
It's not as fast or as expensive as random access memory. It's faster than a hard disk drive. A lot faster. It's more expensive than a hard disk drive. A lot more expensive.

If we are configuring an HP DL980 G7 server, it will cost $4,199 for a 400GB SAS MLC drive or $7,419 for a 400GB SAS SLC drive. That is $10-18 / GB. It's a performance / size trade-off. While SLC drives often perform better, MLC drives are often available in larger sizes. Further, the read / write performance is either symmetric or asymmetric.

That, and SLC drives often have greater endurance.


Sequential
Read
(MB/s)
Sequential
Write
(MB/s)
Random
Read
(IOPS)
Random
Write
(IOPS)
Intel 520 (480GB) 550 520 50,000 50,000
Intel 520 (240GB) 550 520 50,000 80,000
Intel DC S3700 500 460 75,000 36,000

The performance of solid state drives can vary:

  • consumer / enterprise
  • MLC / eMLC / SLC
  • SATA / SAS / PCIe

The capacity of enterprise solid state drives is often less than that of enterprise hard disk drives (4TB). However, the capacity of PCIe drives such as the Fusion-io ioDrive Octal (5.12TB / 10.24TB) is greater than that of enterprise hard disk drives (4TB). In addition, the performance of PCIe drives is greater than that of SAS or SATA drives.


Sequential
Read
(MB/s)
Sequential
Write
(MB/s)
Random
Read
(IOPS)
Random
Write
(IOPS)
Intel 910 (800GB) 2,000 1,000 180,000 75,000

Hard Disk Drive

It may not be fast, but it is inexpensive.

If we are configuring an HP DL980 G7 server, it will cost $309 for a 300GB 10K drive or $649 for a 300GB 15K drive. That is $1-2 / GB. It's a performance / size trade-off. While a 15K drive will perform better than a 10K drive, it will often have less capacity. The sequential read / write performance of hard disk drives is often between 150-200MB/s. As such, a RAID configuration may be a cost effective alternative to a single solid state drive for sequential read / write access.

The capacity of enterprise hard disk drives (4TB) is often greater than that of enterprise solid state drives.

Data Structure
Hash Table

JBoss Data Grid is an in-memory data grid with the data stored in a hash table. However, JBoss Data Grid supports persistence via write-behind or write-through. For all intents and purposes (e.g. map / reduce), all of the data should fit in memory.

Access

  • Random Reads, Random Writes

Riak is a key / value store. If persistence has been configured with Bitcast, the data is stored in a log structured hash table. An in-memory hash table contains the key / value pointers. The value is a pointer to the data. As such, all of the key / value pointers must fit in memory. The data is persisted via append only log files.

Access

  • Complex Index in Memory
  • Random Reads, Sequential Writes

Point queries perform well in hash tables. Range queries do not. Though there is always map / reduce.

B-Tree
MongoDB is a document database with the data stored in a B-Tree. The data is persisted via memory mapped files.

Access

  • Partial Index (Internal Nodes) in Memory
  • Random Reads, Sequential Reads, Random Writes

CouchDB is a document database with the data stored in a B+Tree. The data is persisted via append only log files.

Access

  • Partial Index in Memory
  • Random Reads, Sequential Reads, Sequential Writes

In a B+ Tree, the data is only stored in the leaf nodes. In a B-Tree, the data is stored in both the internal nodes and the leaf nodes. The advantage of a B+ Tree is that the leaf nodes are linked. As a result, range queries perform better with a B+ Tree. However, point queries perform better with a B-Tree.

CouchDB has implemented an append only B+ Tree. An alternative is the copy-on-write (CoW) B+ Tree. A write optimization for a B-Tree is buffering. First, the data written to an internal buffer in an internal node. Second, the buffer is flushed to a leaf node. As a result, random writes are turned in to sequential writes. The cost of random writes is thus amortized.  However, I am not aware of any open source data stores that have implemented a CoW B+ Tree or have implemented buffering with a B-Tree.

Range queries perform well with a B/B+ Tree. Point queries, not as well as hash tables.

Log Structured Merge Tree
Apache HBase and Apache Cassandra are both column oriented data stores, and they have both store data in an LSM-Tree. Apache HBase has implemented a cache oblivious lookahead array (COLA). Apache Cassandra has implemented a sorted array merge tree (SAMT).

In both implementations, a write is first written to a write-ahead log. Next, it is written to a memtable. A memtable is an in-memory sorted string table (SSTable). Later, the memtable is flushed and persisted as an SSTable. As result, random writes are turned in to sequential writes. However, a point query with an LSM-Tree may require multiple random reads.

Apache HBase implemented a single-level index with HFile version 1. However, because every index was cached, it resulted in high memory usage.

Apache HBase implemented a multi-level index a la a B+ Tree with HFile (SSTable) version 2. The SSTable contains a root index, a root index with leaf indexes, or a root index with an intermediate index and leaf indexes. The root index is stored in memory. The intermediate and leaf indexes may be stored in the block cache. In addition, the SSTable contains a compound (block level) bloom filter. The bloom filter is used to determine if the data is not in the data block.

Recommendation / Access

  • Partial Index / Bloom Filter in Memory
  • Random Reads, Sequential Reads, Sequential Writes

A read optimization for an LSM-Tree is fractional cascading. The idea is that each level contains both data and pointers to data in the next level. However, I am not aware of any open source data stores that have implemented fractional cascading.

I like the idea of a hybrid / tiered storage solution for an LSM-Tree implementation with the first level in memory, second level on solid state drives, and third level on hard disk drives. I've seen this solution described in academia, but I am not aware of any open source implementations.

Conclusion
I find it interesting that key / value stores often store data in a hash table, that document stores often store data in a B+/B-Tree, and that column oriented stores often store data in an LSM-Tree. Perhaps it is because key / value stores focus on the performance of point queries, document stores support secondary indexes (MongoDB) / views  (CouchDB), and column oriented stores support range queries. Perhaps it because document stores were not created with distribution (shards / partitions) in mind and thus assume that the complete index can not be stored in memory.

Notes
I found this paper to be very helpful in examining data structures as it covers most of the ones highlighted in this post:

Efficient, Scalable, and Versatile Application and System Transaction Management for Direct Storage Layers (link)

Read the original blog entry...

More Stories By Daniel Thompson

I curate the content on this page, but the credit goes to my talented colleagues for the posts that you see here. Much of what you read on this page is the work of friends at How to JBoss, and I encourage you to drop by the site at http://www.howtojboss.com for some of the best JBoss technical and non-technical content for developers, architects and technology executives on the Web.

@CloudExpo Stories
The definition of IoT is not new, in fact it’s been around for over a decade. What has changed is the public's awareness that the technology we use on a daily basis has caught up on the vision of an always on, always connected world. If you look into the details of what comprises the IoT, you’ll see that it includes everything from cloud computing, Big Data analytics, “Things,” Web communication, applications, network, storage, etc. It is essentially including everything connected online from ha...
We are all here because we are sold on the transformative promise of The Cloud. But what good is all of this ephemeral, on-demand infrastructure if your usage doesn't actually improve the agility and speed of your business? How must Operations adapt in order to avoid stifling your Cloud initiative? In his session at DevOps Summit, Damon Edwards, co-founder and managing partner of the DTO Solutions, will highlight the successful organizational, process, and tooling patterns of high-performing c...
Software-driven innovation is becoming a primary approach to how businesses create and deliver new value to customers. A survey of 400 business and IT executives by the IBM Institute for Business Value showed businesses that are more effective at software delivery are also more profitable than their peers nearly 70 percent of the time (1). DevOps provides a way for businesses to remain competitive, applying lean and agile principles to software development to speed the delivery of software that ...
Docker offers a new, lightweight approach to application portability. Applications are shipped using a common container format and managed with a high-level API. Their processes run within isolated namespaces that abstract the operating environment independently of the distribution, versions, network setup, and other details of this environment. This "containerization" has often been nicknamed "the new virtualization." But containers are more than lightweight virtual machines. Beyond their small...
The move in recent years to cloud computing services and architectures has added significant pace to the application development and deployment environment. When enterprise IT can spin up large computing instances in just minutes, developers can also design and deploy in small time frames that were unimaginable a few years ago. The consequent move toward lean, agile, and fast development leads to the need for the development and operations sides to work very closely together. Thus, DevOps become...
Cloud Expo 2014 TV commercials will feature @ThingsExpo, which was launched in June, 2014 at New York City's Javits Center as the largest 'Internet of Things' event in the world.

ARMONK, N.Y., Nov. 20, 2014 /PRNewswire/ --  IBM (NYSE: IBM) today announced that it is bringing a greater level of control, security and flexibility to cloud-based application development and delivery with a single-tenant version of Bluemix, IBM's

An entirely new security model is needed for the Internet of Things, or is it? Can we save some old and tested controls for this new and different environment? In his session at @ThingsExpo, New York's at the Javits Center, Davi Ottenheimer, EMC Senior Director of Trust, reviewed hands-on lessons with IoT devices and reveal a new risk balance you might not expect. Davi Ottenheimer, EMC Senior Director of Trust, has more than nineteen years' experience managing global security operations and asse...
The major cloud platforms defy a simple, side-by-side analysis. Each of the major IaaS public-cloud platforms offers their own unique strengths and functionality. Options for on-site private cloud are diverse as well, and must be designed and deployed while taking existing legacy architecture and infrastructure into account. Then the reality is that most enterprises are embarking on a hybrid cloud strategy and programs. In this Power Panel at 15th Cloud Expo (http://www.CloudComputingExpo.com...
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at Internet of @ThingsExpo, James Kirkland, Chief Ar...
Leysin American School is an exclusive, private boarding school located in Leysin, Switzerland. Leysin selected an OpenStack-powered, private cloud as a service to manage multiple applications and provide development environments for students across the institution. Seeking to meet rigid data sovereignty and data integrity requirements while offering flexible, on-demand cloud resources to users, Leysin identified OpenStack as the clear choice to round out the school's cloud strategy. Additional...
Technology is enabling a new approach to collecting and using data. This approach, commonly referred to as the "Internet of Things" (IoT), enables businesses to use real-time data from all sorts of things including machines, devices and sensors to make better decisions, improve customer service, and lower the risk in the creation of new revenue opportunities. In his General Session at Internet of @ThingsExpo, Dave Wagstaff, Vice President and Chief Architect at BSQUARE Corporation, discuss the ...
The security devil is always in the details of the attack: the ones you've endured, the ones you prepare yourself to fend off, and the ones that, you fear, will catch you completely unaware and defenseless. The Internet of Things (IoT) is nothing if not an endless proliferation of details. It's the vision of a world in which continuous Internet connectivity and addressability is embedded into a growing range of human artifacts, into the natural world, and even into our smartphones, appliances, a...
"BSQUARE is in the business of selling software solutions for smart connected devices. It's obvious that IoT has moved from being a technology to being a fundamental part of business, and in the last 18 months people have said let's figure out how to do it and let's put some focus on it, " explained Dave Wagstaff, VP & Chief Architect, at BSQUARE Corporation, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
The 4th International DevOps Summit, co-located with16th International Cloud Expo – being held June 9-11, 2015, at the Javits Center in New York City, NY – announces that its Call for Papers is now open. Born out of proven success in agile development, cloud computing, and process automation, DevOps is a macro trend you cannot afford to miss. From showcase success stories from early adopters and web-scale businesses, DevOps is expanding to organizations of all sizes, including the world's large...
Verizon Enterprise Solutions is simplifying the cloud-purchasing experience for its clients, with the launch of Verizon Cloud Marketplace, a key foundational component of the company's robust ecosystem of enterprise-class technologies. The online storefront will initially feature pre-built cloud-based services from AppDynamics, Hitachi Data Systems, Juniper Networks, PfSense and Tervela. Available globally to enterprises using Verizon Cloud, Verizon Cloud Marketplace provides a one-stop shop fo...
"Our premise is Docker is not enough. That's not a bad thing - we actually love Docker. At ActiveState all our products are based on open source technology and Docker is an up-and-coming piece of open source technology," explained Bart Copeland, President & CEO of ActiveState Software, in this SYS-CON.tv interview at DevOps Summit at Cloud Expo®, held Nov 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
DevOps Summit 2015 New York, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that it is now accepting Keynote Proposals. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long development cycles that produce software that is obsolete...
Infor has announced a new feature Infor CloudSuite™ Aerospace & Defense (A&D) to aid compliance with International Traffic in Arms Regulations (ITAR). The ITAR function will serve as a complementary function for new or existing Infor CloudSuite A&D customers, to facilitate compliance for Infor customers that are creating a US defense article or performing a US defense service and wish to benefit from cloud-services. The ITAR regulation serves to manage handling and access requirements for dat...
What do a firewall and a fortress have in common? They are no longer strong enough to protect the valuables housed inside. Like the walls of an old fortress, the cracks in the firewall are allowing the bad guys to slip in - unannounced and unnoticed. By the time these thieves get in, the damage is already done and the network is already compromised. Intellectual property is easily slipped out the back door leaving no trace of forced entry. If we want to reign in on these cybercriminals, it's hig...