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Toshiba PX04S 12Gb/s SAS Enterprise SSD Review

Toshiba PX04S 12Gb/s SAS Enterprise SSD Review

Toshiba brings the fastest SAS SSD ever to grace the 12Gb/s connection in its PX04S, which tops out over 300,000 IOPS in our testing and comes in capacities up to 3.84TB.

The enterprise SSD market is fragmented into three key sections: PCIe, SAS and SATA. SAS began its journey in the datacenter a little over a decade ago, and the tried and true "Ethernet of storage" has weathered the storms of change while continuing to evolve and increase its capabilities with each successive generation.

NVMe PCIe SSDs attract the press flashbulbs, but in reality they only constitute a sliver of the actual SSD deployments. NVMe will surely pick up as time wears on, but in the meantime SAS continues to thrive in the datacenter. SAS faces competitors from the low-end SATA and high-end PCIe SSDs, but recent reports indicate that SAS SSDs shipments in Q1 2015 were nearly double that of Q1 2014.

The move to 12Gb/s SAS provided the industry with an enhanced fabric that supports box-to-box, server-to-storage, and rack-to-rack connections. Coupling 12Gb/s SAS with switches and expanders bolsters the expanded set of topology options -- and active copper and optical connections fuel the expansion of the SAS ecosystem over greater distances.

12Gb/s SAS provides more speed than its SATA counterpart does, not to mention mission-critical capabilities. The first-generation 12Gb/s SAS SSDs were impressive, but they couldn't push the protocol to the limit. It's common sense that individual HDDs cannot scratch at the speed provided by 12Gb/s SAS (with the exception of cache/SSHD burst), but with SSDs we expect them to fully utilize the connection.

Toshiba's new 12Gb/s SAS PX04S Series SSD picks up the gauntlet with impressive top-line specs up to 270,000 read IOPS and 125,000 random write IOPS. Sequential performance weighs in at up to 1,900/850 MB/s read/write, and the SSDs run the gamut from 200GB all the way up to 3.84TB of user-addressable capacity.

12Gb/s SAS Dual-Port Mode PX04SHB PX04SMB
Endurance25 DWPD10 DWPD3 DWPD1 DWPD
Capacity200, 400, 800GB, 1.6TB400, 800GB, 1.6TB, 3.2TB480, 960GB, 1.92, 3.84TB480, 960GB, 1.92, 3.84TB
Power (Active/Idle)9.0-9.5W / 3.2W9.0-9.5W / 3.2W9.0-9.5W / 3.2W9.0-9.5W / 3.2W
9 Watt - 64KiB Seq Read MiB/s1900 MiB/s
(1500 1.6TB)
1900 MiB/s
(1500 3.2TB)
1900 MiB/s
(1500 3.84TB)
1900 MiB/s
(1500 3.84TB)
12 Watt - 64KiB Seq Read MiB/s1900 MiB/s1900 MiB/s
1900 MiB/s1900 MiB/s
9 Watt - 64KiB Seq Write MiB/s850 MiB/s
(750 1.6TB)
850 MiB/s
(750 3.2TB)
850 MiB/s
(750 3.84TB)
850 MiB/s
(750 3.84TB)
12 Watt - 64KiB Seq Write MiB/s1100 MiB/s1100 MiB/s
1100 MiB/s1100 MiB/s
9 Watt - 4KiB Random Read270,000 IOPS270,000 IOPS
270,000 IOPS270,000 IOPS
12 Watt - 4KiB Random Read 270,000 IOPS270,000 IOPS
270,000 IOPS270,000 IOPS
9 Watt - 4KiB Random Write125,000 IOPS90,000 IOPS
(85K 3.2TB)
60,000 IOPS
(55K 3.84TB)
22,000 IOPS
12 Watt- 4KiB Random Write165,000 IOPS115,000 IOPS
72,000 IOPS26,000 IOPS

The SSDs come in a variety of flavors, with high endurance (PX04SHB), mid endurance (PX04SMB), value endurance (PX04SVB) and read intensive (PX04SRB) SSDs available for the varied workloads in the datacenter. The falling cost of flash enables competitive price points for the read-centric segment, and the value-centric models bring the SCSI command set and all of the mission-critical features of SAS, such as multi-path and failover, at a more palatable price point.

Toshiba's high performance specifications immediately raise the question if the PX04S operates in wide-port mode during dual-port operation. The PX04S does not support wideport functionality at this time, and instead utilizes a narrow-port active-active configuration that allows both ports to operate simultaneously and independently at full speed. The SSD is rated for a maximum of 270,000 random read IOPS in dual-port, but in our testing we easily beat those metrics by 67,000 IOPS.

Toshiba A19nm eMLC NAND powers the PX04S Series and overprovisioning weighs in at either 28 or 56 percent, depending upon the endurance of the model. Toshiba utilizes an 18-channel co-branded Toshiba/Marvell controller on the PX04S that has the robust Toshiba feature set, including its proprietary QSBC (Quadruple Swing-by Code) error correction. We cover QSBC on the following page.


The PX04S SSDs can operate in either a standard 9W mode or a performance-oriented 12W mode. The 12 watt mode unlocks the true performance capabilities of the SSD by providing enhanced performance in any type of write workload, including demanding mixed workloads.

The ability to dial back the power consumption increases the efficiency of the SSD and lowers the SSD's thermal characteristics. This is incredibly helpful in dense architectures where heat can become problematic, and also satisfies operators with strict efficiency requirements. The high performance specifications ensure the PX04S offers a very refined IOPS-per-Watt rating; and with its PCIe-like speed, the PX04S is actually more efficient than the leading PCIe SSDs, which tend to pull over 25W to deliver comparable performance metrics. We measure power and efficiency extensively in our tests.

The PX04S has enhanced ability to recover due to an internal RAID 6-like implementation that can sustain the loss of up to two entire dies. The SSD also features enhanced power loss protection, end-to-end data protection, a 2 million hour MTTF, a 1 sector per 10^17 UBER rating and a five-year warranty. Time to tear it apart.

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