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DELL PERC H700 and H800 Technical Guide 10
Other new features of the 6Gb/s SAS controllers will offer improved signal integrity and additional
safeguards to enhance data protection with support for SED (Self-Encrypting Drive) technology.
Table 2. 6Gb/s SAS (SAS 2.0) Features
DAS-based
Server Storage
6Gb/s Throughput
3Gb/s Compatible
Standard Mini-SAS Connectors (SFF-8087
and SFF-8088)
DFE (Decision Feedback Equalization)
improved signaling
SSC (Spread Spectrum Clocking) reduced
radiated emissions
Enhanced Security with SED (Self-
Encrypting Drive) support
Improved Scalability
2.2.1 6Gb/s SAS Performance Benefit over 3Gb/s SAS
In small disk drive configurations (one to eight drives) the aggregate media rate of the disks (the
speed at which the disk heads can read and write data) become the bottleneck for storage
throughput. As business storage needs grow, IT centers can add more disk drives to their storage
infrastructure, and the latest generation of SAS allows server performance to scale past the 3Gb/s
SAS performance limitations: from 2.4 GB/s to 4.8 GB/s unidirectional.
Table 3. SAS Performance Details
SAS Generation
PCI-Express
Interface
Approximate number of SAS
HDDs required saturate
bandwidth (RAID 0)
1.0 (3Gb)
1.0
8 to10
2.0 (6Gb)
2.0
16 to 20
In addition to the improvements in the SAS bandwidth, PCI Express 2.0 provides double the system-
to-storage controller interconnect speed. The x8 PCI Express 1.0 interface linking the controller to
the host platform limited throughput even further to a theoretical 2GB/s maximum, that limitation
has been raised to 4GB/s (unidirectional).
2.2.2 6Gb/s SAS Expectation
RAID controllers employing 6Gb/s SAS technology excel in both high IOP and high bandwidth
applications. Applications and environments that benefit most range from traditional data center
applications (such as random IOPs intensive email, web and database servers) to streaming and
archival applications that will benefit from improved sequential read and write throughput. This
means more users, more video streams, more email accounts, and faster backups are now possible.