Pcie Raid And Ssd Sas Adapter - IBM Power 720 Overview

For detailed information about SAS cabling of external storage, see the IBM Power Systems
Hardware information center:
http://publib.boulder.ibm.com/infocenter/powersys/v3r1m5/index.jsp
Table 2-14 compares features of parallel SCSI and SAS.
Table 2-14 Comparison parallel SCSI to SAS
Feature
Architecture
Performance
Scalability
Compatibility
Max. cable length
Cable from factor
Hot pluggability
Device identification
Termination

2.7.6 PCIe RAID and SSD SAS Adapter

A new SSD option for selected POWER7 and POWER7+ processor-based servers offers a
significant price-for-performance improvement for many client SSD configurations. The new
SSD option is packaged differently from those currently available with Power Systems. The
new PCIe RAID and SSD SAS adapter has up to four 177 GB SSD modules, plugged directly
onto the adapter, saving the need for the SAS bays and cabling that are associated with the
current SSD offering. The new PCIe-based SSD offering can save up to 70% of the list price,
and reduce up to 65% of the footprint, compared to disk enclosure based SSD, assuming
equivalent capacity. This benefit is dependant on the configuration required.
Parallel SCSI
Parallel, all devices connected to
shared bus
320 MBps (Ultra320 SCSI),
performance degrades as devices
added to shared bus
15 drives
Incompatible with all other drive
interfaces
12 meters total (must sum lengths of
all cables used on bus)
Multitude of conductors adds bulk,
cost
Yes
Manually set, user must ensure no
ID number conflicts on bus
Manually set, user must ensure
proper installation and functionality
of terminators
Chapter 2. Architecture and technical overview
SAS
Serial, point-to-point, discrete signal
paths
3 Gbps, roadmap to 12 Gbps,
performance maintained as more
devices added
Over 16,000 drives
Compatible with Serial ATA (SATA)
8 meters per discrete connection,
total domain cabling hundreds of
meters
Compact connectors and cabling
save space, cost
Yes
Worldwide unique ID set at time of
manufacture
Discrete signal paths enable device
to include termination by default
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