Series 7 Architecture
One of the immediate goals for the engineers at PMC-Sierra was to create a controller to saturate the PCIe 3.0 connection. PCIe Gen3 offers a tremendous amount of bandwidth and saturating that is simply not possible with existing solutions. Typical RAID architectures consist of 8 x 6Gb/s SAS ports. This provides a limited pathway for the controller, topping out at 4.8 GB/s of useable bandwidth.
The PM8015 ROC features 24 x 6Gb/s SAS native ports combined with the x8 PCIe Gen3 interface. 16 ports alone can saturate the bus by providing 9.8 GB/s, well above the 8 GB/s supplied by PCIe Gen3. This allows Adaptec to pack as many lanes on board a small form-factor card as possible. The resulting Low Profile/MD-2 ASR-71605 provides an unmatched 16 ports of SAS/SATA connectivity in the half-height category, and the ASR-71405 that we are testing today features an unmatched 24 native SAS/SATA ports in the full-height half-length category.
One great feature of the ASR-72405 that we were repeatedly thankful for during testing is the ability to switch the controller into HBA mode. This functionality allows users to switch the adapter from RAID to HBA mode. After a reboot, the attached devices are presented to the host directly. In terms of device management, this is extremely useful.
The Adaptec Series 7 controllers boast impressive specifications. With a RAID 0 configuration with 24x SSDs, Adaptec observed 534,000 IOPS with a 4k random read workload. The maximum 4k write IOPS recorded with the same configuration totaled 374,000 IOPS. The maximum 1MB sequential read speed weighed in at 6,400 MB/s and sequential write speed was clocked of 5229 MB/s. With the 512B file size sequential data transfers topped 1.02 million IOPS, and the write speed topped out at 1.07 million IOPS.
With a RAID 5 configuration, the Series 7 adapters perform at up to 6.6 GB/s with sequential read and 2.6 GB/s in sequential write. With 16 direct connected SSDs they delivered 450,000 IOPS.
Adaptec RAID Code (ARC) delivers RAID levels 0, 1, 1E, 5, 6, 10, 50 and 60 (71605E supports 0, 1, 1E, and 10, only). ARC also offers RAID Level Migration (the ability to easily migrate RAID levels), Online Capacity Expansion (expand capacity without powering down the server), and Copyback Hot Spare (when a failed drive has been replaced, data is automatically copied from the hot spare back to the restored drive).
Adaptec's Intelligent Power Management techniques can purportedly reduce storage power consumption, and thus cost, by up to 70%. This is enabled by shifting the power for the connected devices into one of three modes; full on, low power and spin down.
The controllers are rated for 700,000 hours MTBF at 40C, though it is noted that they are still undergoing testing, and this number may increase. The adapter carries a standard three year warranty.
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