Welcome!

Cloud Expo Authors: Yeshim Deniz, Jason Bloomberg, Hovhannes Avoyan, Brian Lavallée, Roger Strukhoff

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.

Cloud Expo Latest Stories
Hardware will never be more valuable than on the day it hits your loading dock. Each day new servers are not deployed to production the business is losing money. While Moore’s Law is typically cited to explain the exponential density growth of chips, a critical consequence of this is rapid depreciation of servers. The hardware for clustered systems (e.g., Hadoop, OpenStack) tends to be significant capital expenses. In his session at 15th Cloud Expo, Mason Katz, CTO and co-founder of StackIQ, to discuss how infrastructure teams should be aware of the capitalization and depreciation model of these expenses to fully understand when and where automation is critical.
Over the last few years the healthcare ecosystem has revolved around innovations in Electronic Health Record (HER) based systems. This evolution has helped us achieve much desired interoperability. Now the focus is shifting to other equally important aspects – scalability and performance. While applying cloud computing environments to the EHR systems, a special consideration needs to be given to the cloud enablement of Veterans Health Information Systems and Technology Architecture (VistA), i.e., the largest single medical system in the United States.
In his session at 15th Cloud Expo, Mark Hinkle, Senior Director, Open Source Solutions at Citrix Systems Inc., will provide overview of the open source software that can be used to deploy and manage a cloud computing environment. He will include information on storage, networking(e.g., OpenDaylight) and compute virtualization (Xen, KVM, LXC) and the orchestration(Apache CloudStack, OpenStack) of the three to build their own cloud services. Speaker Bio: Mark Hinkle is the Senior Director, Open Source Solutions, at Citrix Systems Inc. He joined Citrix as a result of their July 2011 acquisition of Cloud.com where he was their Vice President of Community. He is currently responsible for Citrix open source efforts around the open source cloud computing platform, Apache CloudStack and the Xen Hypervisor. Previously he was the VP of Community at Zenoss Inc., a producer of the open source application, server, and network management software, where he grew the Zenoss Core project to over 10...
Most of today’s hardware manufacturers are building servers with at least one SATA Port, but not every systems engineer utilizes them. This is considered a loss in the game of maximizing potential storage space in a fixed unit. The SATADOM Series was created by Innodisk as a high-performance, small form factor boot drive with low power consumption to be plugged into the unused SATA port on your server board as an alternative to hard drive or USB boot-up. Built for 1U systems, this powerful device is smaller than a one dollar coin, and frees up otherwise dead space on your motherboard. To meet the requirements of tomorrow’s cloud hardware, Innodisk invested internal R&D resources to develop our SATA III series of products. The SATA III SATADOM boasts 500/180MBs R/W Speeds respectively, or double R/W Speed of SATA II products.
14th International Cloud Expo, held on June 10–12, 2014 at the Javits Center in New York City, featured three content-packed days with a rich array of sessions about the business and technical value of cloud computing, Internet of Things, Big Data, and DevOps led by exceptional speakers from every sector of the IT ecosystem. The Cloud Expo series is the fastest-growing Enterprise IT event in the past 10 years, devoted to every aspect of delivering massively scalable enterprise IT as a service.
As more applications and services move "to the cloud" (public or on-premise) cloud environments are increasingly adopting and building out traditional enterprise features. This in turn is enabling and encouraging cloud adoption from enterprise users. In many ways the definition is blurring as features like continuous operation, geo-distribution or on-demand capacity become the norm. NuoDB is involved in both building enterprise software and using enterprise cloud capabilities. In his session at 15th Cloud Expo, Seth Proctor, CTO at NuoDB, Inc., will discuss the experiences from building, deploying and using enterprise services and suggest some ways to approach moving enterprise applications into a cloud model.
Until recently, many organizations required specialized departments to perform mapping and geospatial analysis, and they used Esri on-premise solutions for that work. In his session at 15th Cloud Expo, Dave Peters, author of the Esri Press book Building a GIS, System Architecture Design Strategies for Managers, will discuss how Esri has successfully included the cloud as a fully integrated SaaS expansion of the ArcGIS mapping platform. Organizations that have incorporated Esri cloud-based applications and content within their business models are reaping huge benefits by directly leveraging cloud-based mapping and analysis capabilities within their existing enterprise investments. The ArcGIS mapping platform includes cloud-based content management and information resources to more widely, efficiently, and affordably deliver real-time actionable information and analysis capabilities to your organization.
Almost everyone sees the potential of Internet of Things but how can businesses truly unlock that potential. The key will be in the ability to discover business insight in the midst of an ocean of Big Data generated from billions of embedded devices via Systems of Discover. Businesses will also need to ensure that they can sustain that insight by leveraging the cloud for global reach, scale and elasticity. In his session at Internet of @ThingsExpo, Mac Devine, Distinguished Engineer at IBM, will discuss bringing these three elements together via Systems of Discover.
Cloud and Big Data present unique dilemmas: embracing the benefits of these new technologies while maintaining the security of your organization’s assets. When an outside party owns, controls and manages your infrastructure and computational resources, how can you be assured that sensitive data remains private and secure? How do you best protect data in mixed use cloud and big data infrastructure sets? Can you still satisfy the full range of reporting, compliance and regulatory requirements? In his session at 15th Cloud Expo, Derek Tumulak, Vice President of Product Management at Vormetric, will discuss how to address data security in cloud and Big Data environments so that your organization isn’t next week’s data breach headline.
The cloud is everywhere and growing, and with it SaaS has become an accepted means for software delivery. SaaS is more than just a technology, it is a thriving business model estimated to be worth around $53 billion dollars by 2015, according to IDC. The question is – how do you build and scale a profitable SaaS business model? In his session at 15th Cloud Expo, Jason Cumberland, Vice President, SaaS Solutions at Dimension Data, will give the audience an understanding of common mistakes businesses make when transitioning to SaaS; how to avoid them; and how to build a profitable and scalable SaaS business.
SYS-CON Events announced today that Gridstore™, the leader in software-defined storage (SDS) purpose-built for Windows Servers and Hyper-V, will exhibit at SYS-CON's 15th International Cloud Expo®, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Gridstore™ is the leader in software-defined storage purpose built for virtualization that is designed to accelerate applications in virtualized environments. Using its patented Server-Side Virtual Controller™ Technology (SVCT) to eliminate the I/O blender effect and accelerate applications Gridstore delivers vmOptimized™ Storage that self-optimizes to each application or VM across both virtual and physical environments. Leveraging a grid architecture, Gridstore delivers the first end-to-end storage QoS to ensure the most important App or VM performance is never compromised. The storage grid, that uses Gridstore’s performance optimized nodes or capacity optimized nodes, starts with as few a...
SYS-CON Events announced today that Solgenia, the global market leader in Cloud Collaboration and Cloud Infrastructure software solutions, will exhibit at SYS-CON's 15th International Cloud Expo®, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Solgenia is the global market leader in Cloud Collaboration and Cloud Infrastructure software solutions. Designed to “Bridge the Gap” between personal and professional social, mobile and cloud user experiences, our solutions help large and medium-sized organizations dramatically improve productivity, reduce collaboration costs, and increase the overall enterprise value by bringing collaboration and infrastructure solutions to the cloud.
Cloud computing started a technology revolution; now DevOps is driving that revolution forward. By enabling new approaches to service delivery, cloud and DevOps together are delivering even greater speed, agility, and efficiency. No wonder leading innovators are adopting DevOps and cloud together! In his session at DevOps Summit, Andi Mann, Vice President of Strategic Solutions at CA Technologies, will explore the synergies in these two approaches, with practical tips, techniques, research data, war stories, case studies, and recommendations.
Enterprises require the performance, agility and on-demand access of the public cloud, and the management, security and compatibility of the private cloud. The solution? In his session at 15th Cloud Expo, Simone Brunozzi, VP and Chief Technologist(global role) for VMware, will explore how to unlock the power of the hybrid cloud and the steps to get there. He'll discuss the challenges that conventional approaches to both public and private cloud computing, and outline the tough decisions that must be made to accelerate the journey to the hybrid cloud. As part of the transition, an Infrastructure-as-a-Service model will enable enterprise IT to build services beyond their data center while owning what gets moved, when to move it, and for how long. IT can then move forward on what matters most to the organization that it supports – availability, agility and efficiency.
Every healthy ecosystem is diverse. This is especially true in cloud ecosystems, where portability and interoperability are more important than old enterprise models of proprietary ownership. In his session at 15th Cloud Expo, Mark Baker, Server Product Manager at Canonical/Ubuntu, will discuss how single vendors used to take the lead in creating and delivering technology, but in a cloud economy, where users want tools of their preference, when and where they need them, it makes no sense.