Developing AdvancedTCA Systems with Large Storage Requirements

By Brian Carr, Emerson Network Power

AdvancedTCA is being adopted for server-based applications with large storage requirements, such as billing engines, authentication databases, service delivery platforms, and IPTV content caching. These applications can roughly be divided into ones involving databases and ones involving content and streaming storage.

Typically used with software such as Oracle, a database storage application holds customer and session data for use in billing engines. Capacity needs are moderate, typically less than 4 Terabytes, and random access read/write performance and write latency are particularly critical characteristics.

Content and streaming storage applications access media files and related user storage. Examples include video mail, audio ring tones, and local cache files for IPTV. Predictable delivery of large digital media files to customer endpoints is the key here.

The diversity of needs means that there is no universal solution. Instead, vendors offer a tiered strategy so the customer can choose the appropriate capacity, performance, topology, and price point. The same approach can be taken for AdvancedTCA-based systems.

Storage Topologies
There are two basic storage architectures:  direct attached and shared. Each can be in-shelf or connected to external arrays.

Direct Attached Storage (In-Shelf)
One can attach up to four individually hot-swappable 2.5” drives to an AdvancedTCA front blade, and an RTM allows for two more. Using a JBOD (“Just a Bunch of Disks”) configuration, these can be daisy chained to other blades. In this topology, the CPU blade handles RAID management and allows two blades to access the storage.

Direct Attached Storage (External)
For applications requiring more capacity without needing access from more than one or two CPU blades, a simple cost-effective external storage array can be utilized. This is typically implemented via SAS connections available on server-class CPU blades.

Shared Storage (In-shelf)
To access shared storage from multiple CPU blades, one can use a specialist storage blade serving data across the AdvancedTCA fabric interface via iSCSI protocols. The storage capacity is the same as for JBOD, but without the complicated external SAS cabling. Storage blades can also provide sophisticated RAID controllers and iSCSI accelerator chips that improve performance.

Shared Storage (External)
External shared storage provides access to common data via either Fibre Channel or Ethernet/iSCSI. Advantages include the ability to use larger drives and multiple Fibre Channel connections for improved streaming performance. By using sophisticated RAID controllers and management software, external storage arrays can divide large capacity among many CPU blades.

Solution Matching
For large database storage applications, direct attached or shared solutions are preferable, depending on how many CPU blades require access. JBOD blades can be used for applications requiring single/dual blade access, and shared storage blades for ones requiring access from multiple CPU blades.

For large content supply applications, the best option is an external, shared storage solution based on multiple Fibre Channel connections or many high capacity, high RPM drives. As solid state drives become cheaper, they can provide still other variations.

Brian Carr is Marketing Manager for Embedded Computing at Emerson Network Power. You can reach him at brian.carr@emerson.com.