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SAS Is Alive And Kicking With Toshiba's PX04SL SSD

By - Source: Toshiba
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Toshiba's new PX04SL 12 Gbps SAS SSD extends the company's PXO4S series of SSDs into the read-centric segment, which is commonly viewed as the SATA stomping grounds. Toshiba's latest SSD is available in up to 4 TB capacities and features 270,000/19,000 random read/write IOPS and up to 1,900/850 MiBps of sequential read/write speed.

Historically, SAS HDDs have been associated with a higher price point. Contrary to popular belief, other components contributed the lion's share of the SAS premium, and not the interface itself. With HDDs, SAS incurred a price penalty because vendors constructed the drives of materials that were more robust and featured higher RPM specifications. In contrast, an SSD's physical components are very similar to SATA products, and thus the price delta between SAS and SATA SSDs is not as pronounced - although it still exists.

Many have predicted that the low-cost and low-endurance segment will gravitate around the SATA interface, while high-performance workloads will migrate to the faster NVMe interface. This prediction has not played out for several reasons. The latest generation of 12 Gbps SAS SSDs have generated enough performance to remain competitive with their NVMe counterparts, and the continued reduction in the price of SAS SSDs have placed them on a more competitive footing with SATA offerings.

The read-centric segment is exploding; the majority of SSDs released over the last year have been tailor-made for light workloads. The Toshiba PX04SL plants its flag in the low-endurance ground with less than 0.5 DWPD (Drive Writes Per Day) of endurance. This relegates the SSD to read-centric workloads, such as data warehousing, web servers, media streaming and video on demand (VOD).

Combining a lower price point with the benefits of SAS, such as multipath and failover, and the overall PX04S architecture, which boats market leading speeds, has the potential to be powerful. We recently evaluated the PX04SMB, the higher-endurance version of the PX04SL, and found it to offer the best performance in the 12 Gbps SAS SSD segment by a large margin. It is currently our recommended pick in our Best Enterprise SSDs guide.

12Gb/s SAS Dual-Port Mode PX04SHB PX04SMB
Endurance25 DWPD10 DWPD3 DWPD1 DWPD0.5 DWPD
Capacity200, 400, 800GB, 1.6TB400, 800GB, 1.6TB,3.2TB480, 960GB, 1.92, 3.84TB480, 960GB, 1.92, 3.84TB 2, 4 TB
Power (Active/Idle)9.0-9.5W / 3.2W9.0-9.5W / 3.2W9.0-9.5W / 3.2W9.0-9.5W / 3.2W?/3.2W
64KiB Seq Read MiB/s190019001900 19001,900
64KiB Seq Write MiB/s11001100
4KiB Random Read 270,000 IOPS270,000 IOPS
270,000 IOPS270,000 IOPS270,000
4KiB Random Write165,000 IOPS115,000 IOPS
72,000 IOPS26,000 IOPS19,000

The PX04SL offers the same leading speed in sequential and random read workloads, but its lower endurance equates to reduced performance in write workloads. The SSDs feature a tunable power consumption feature, which customizes it for each respective environment. There are also secure erase and self-encrypting models available for the security conscious.

Toshiba exchanged some of the SSD's spare area, known as overprovisioning, for a reduction in endurance. The key to reducing the spare area without affecting the core reliability features boils down to Toshiba's proprietary QSBC (Quadruple Swing-Buy Code), which is more powerful than some LDPC error-correction implementations. This provides a higher capacity point than the other members of the PX04S family. The SSD is geared to compete with other high-capacity read-centric SSDs, and thus is only available in 2 and 4 TB options.

Toshiba's PX04SL highlights the fact that SAS is alive and kicking. The SCSI trade association recently unveiled an expanded SAS roadmap at Storage Visions 2016 that indicates 24 Gbps SAS will come to fruition in 2018. This bodes well for administrators seeking to leverage the benefits of today's architectures with increased performance and functionality in the future.

The PX04SL is available today.

Paul Alcorn is a Contributing Editor for Tom's IT Pro, covering Storage. Follow him on Twitter and Google+.