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Introducing IBM FlashSystem 840

The IBM FlashSystem 840 introduces new availability, scalability and connectivity features to the IBM all-flash array product family. These new features provide higher uptime and configuration flexibility, which position the FlashSystem 840 for data-center-wide implementation.

Why Flash?

The deployment of flash-memory technology is an important new trend in the computing industry. Flash-memory devices can greatly accelerate the performance of many applications through reduced disk access latency and higher I/O operations per second (IOPS). Implementation of flash-memory devices often increases server utilization by reducing wait on I/O. The use of flash-based devices may also reduce the need for read cache on back-end storage systems. Flash-memory technology is deployed in a variety of form factors including traditional disk-drive carriers, memory DIMM slot compatible devices and all-flash arrays.


The FlashSystem 840 is an all-flash array with dual controllers and 12 hot-swappable flash module slots. It’s rated at 1,100,000 IOPS and has a read latency of 135 microseconds. The entire system is configured as all RAID-0 (striping without protection) or all RAID-5 (striping with protection). Enterprise Multilevel cell (eMLC)-based flash modules are available in 1 TB, 2TB and 4TB sizes. Note that different-sized flash modules cannot be mixed within the same system. Systems using 1TB flash modules can be configured with the following useable capacities:

  • RAID-0 (2 TB, 4TB, 6TB, 8TB, 10TB, 12TB)
  • RAID-5 (2TB, 4TB, 6TB, 8TB, 10TB)

Systems using 2TB flash modules can be configured with the following useable capacities:

  • RAID-0 (4TB, 8TB, 16TB, 20TB, 24TB)
  • RAID-5 (4TB, 12TB, 16TB, 20TB)

When using 4TB flash modules, useable capacity options include:

  • RAID-0 (32TB, 40TB, 48TB)
  • RAID-5 (8TB, 24TB, 32TB, 40TB)

If you start out with a smaller configuration, you can hot-add additional flash modules to increase useable capacity to one of those previously listed.

In addition to the RAID-5 disk protection, the FlashSystem 840 features IBM-exclusive Variable Stripe RAID (VSR) technology. VSR provides RAID striping on the flash module. Each flash module has an integrated controller that implements RAID with rotating parity to protect the flash chips on that module. Each module has 10 flash-memory chips, which operate in a 9+1 mode. If one of the chips has a problem, the VSR changes just that module’s RAID array to 8+1. The combination of RAID-5 on the modules along with RAID-5 across all of the flash modules provides two-dimensional RAID protection. The FlashSystem 840 can also be configured with optional AES XTS 256 data-at-rest encryption for data security.

System Design

The FlashSystem 840 is packaged into a space- and power-efficient, 2U rack mount drawer. Designed for high uptime, the FlashSystem 840 features the following hot-swappable, redundant components:

  • Two management modules
  • Up to 12 flash-data storage modules
  • Two power supplies
  • Four fan modules
  • Two battery modules

All of these components are accessed from the front or rear of the unit. The system doesn’t slide out on rails. This simplifies cable routing and reduces service clearances. All cables are connected to the back of the unit. Each of the two management modules contains a RAID controller, two host interface cards and a management controller. The FlashSystem 840 is designed to remain online during all firmware updates.

Connectivity and Management

The IBM FlashSystem can be configured with FC, FCoE or InfiniBand host connections. The total quantity of host connection ports for each type of interface is:

  • 16 ports of 8Gb FC (can also operate at 4Gb)
  • 8 ports of 16Gb FC (can also operate at 8Gb and 4Gb)
  • 16 ports of 10Gb FCoE
  • 8 ports of InfiniBand QDR 40Gb

The host connection ports are divided evenly across the two management modules. FC and FCoE connections are implemented though the use of 4-port host interface cards, which are populated with SFP+ optical transceivers that provide specific connection types and speeds. When configured with 16Gb FC transceivers, ports 3 and 4 on the host interface cards are disabled. Intermixing connectivity types is not permitted within a single system. Active-Active multipathing is supported on all interfaces. Multipathing functionality is dependent upon software support provided by the connected host. Supported hosts include Windows Server 2003/2008, Linux and AIX. In addition to the host connections, each of the two management modules has a 1Gb RJ45 Ethernet port that is used for system configuration and monitoring.

The FlashSystem 840 provides both GUI and command-line access to the management modules. The management modules operate in an active-passive mode. The GUI is accessed using a Web browser and has a similar look and feel to the management interface used with the IBM SAN Volume Controller (SVC) and IBM XIV storage. The management interface is used to define LUNs, create and manage access policies, and for system monitoring. The FlashSystem 840 can be implemented in several ways. Here are two examples:

  • As an additional copy of active data that’s also stored on back-end disk. The flash array provides extremely fast disk read operations with low latency.
  • As Tier-1 storage in a tiered disk environment. Tiering can be automated through the use of SVC or IBM Storwize V7000 disk subsystem.

The FlashSystem 840 provides support for up to 2,048 LUNs.

IBM FlashSystem V840

The IBM FlashSystem V840 is a new IBM product that combines an IBM Flash System 840 system with a pair of SVC units. The V840 provides high performance all-flash array technology and software virtualization in a single, integrated solution. Storage virtualization features provided by the FlashSystem V840 include:

  • The capability to virtualize the FlashSystem 840, traditional IBM storage and third-party storage through a single management console
  • Thin provisioning, application aware copies and data replication
  • Easy Tier that lets flash and HDD technology be combined. Frequently access data will reside on flash and less frequently access data will be moved to HDD
  • Real-time compression to improve utilization
  • Scalable design lets flash and HDD storage capacity be increased to match usage patterns

The FlashSystem V840 elevates flash technology to a new level of functionality and is designed for data-center-wide implementation.

The New Standard in Flash Technology

The FlashSystem 840 provides significant enhancements to the IBM FlashSystem product line. The capability to select 1TB, 2TB or 4TB flash modules balances entry price and high-end capacity. Online firmware updates and hot-swappable flash modules significantly enhance system uptime. And, for a complete data-center solution, the FlashSystem V840 combines all-flash array technology with storage virtualization.

Charlie Cler supports customers in a solutions-architect role at Forsythe Technology Inc. He can be reached at



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