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Choose Your Own Enterprise SSD Adventure: SAS or PCIe NVMe?

 

Growing up, I enjoyed reading the Bantam Books series "Choose Your Own Adventure," where the reader assumed the role of the protagonist and made a series of choices to determine the outcome of the story. In the enterprise SSD world, OEM customers are embarking on an adventure of their own and are on the verge of making a critical choice: SAS or PCIe® NVM Express® (NVMe™)2

It's hard to overstate the importance of choosing an interface for the next generation of enterprise platforms. On the one hand we have SAS, a mature and robust interface which evolved from parallel SCSI and that approximately five years ago saw a significant upgrade to 12Gbit/s, doubling the interface frequency compared to SAS-2 and SATA 6Gbit/s. Server-attached SAS HBAs jumped on the 12Gbit/s bandwagon long ago, but on the storage side, the transition is still happening. There are several key features that make SAS the de-facto standard for enterprise applications such as its time-tested reliability, dual-port, full duplex, multi-initiator point-to-point and multi-path IO capabilities which enable high availability and improved performance as compared to SATA.

On the other hand we have PCIe NVMe, the choice for customers seeking lower average latency. PCIe NVMe SSDs put data closer to the CPU by revamping the physical interface and software stack to optimize access to flash media while maintaining legacy block access for application compatibility. The result is blazing fast speed with latencies achievable below 20 microseconds. The main drawback of PCIe SSDs up to now has been the lack of enterprise hardware support due to lack of features and ecosystem readiness to utilize them. However, this is changing rapidly as features such as dual-port and hot-pluggability are making their way into the latest drives.

1Amber Huffman, NVM Express Overview & Ecosystem Update (Aug, 2013)

Notice I did not mention performance as a major differentiator. People mistakenly believe that SAS is significantly slower than NVMe, but this is no longer the case. Thanks to MultiLink SAS™3, SAS can achieve comparable blazing performance of PCIe SSDs that we’ve come to love.

With all of this in mind, how would a customer make a seemingly impossible decision between the robustness of SAS and the swiftness of PCIe NVMe? Enter Toshiba’s latest enterprise SAS and PCIe SSD offerings: PM5 and CM5.

A couple months ago, Toshiba announced XG5, the first client NVMe drive using Toshiba's 64 layer, 3-bit-per-cell TLC (triple-level cell) BiCS FLASH™. Today, we are following that announcement with the launch of two new enterprise drives also featuring 3D TLC BiCS FLASH. PM5 is Toshiba's next-generation 12Gbit/s SAS drive which follows the award-winning PX05S. CM5 is Toshiba's next iteration of a dual-port NVMe drive following the ZD6300. One of the most remarkable features of the PM5 and CM5 drives is that they share a common back-end firmware, as well as most of the hardware on the drive, enabling customers to share resources between qualification efforts of these two drives.

PM5 builds upon the success of PX04P and delivers blazing speeds between 48% and 150% higher than the previous generation of SSDs while delivering the consistent reliability that customers have come to expect from Toshiba drives by improving the mean time between failures (MTBF) to 2.5M hours and reducing the unrecoverable bit error rate (UBER) to 1E-204.

Metric PX04S PM5 MultiLink Improvement
SR - MB/s5 1,991 3,355

+69%

SW - MB/s6 1,153 2,726

+136%

RR - IOPS78 270,000 400,000

+48%

RW – IOPS9 120,000 300,000

+150%

CM5 is Toshiba’s second dual-port enterprise NVMe drive. However, since it is built on a common back-end firmware and hardware with PM5, it benefits from Toshiba’s long history of quality in SAS. Customers who decide to take on the enterprise NVMe challenge head-on can rest assured that this drive is future-proofed for NVMe over Fabrics (NVMe-oF) thanks to the implementation of scatter gather lists and controller memory buffer. Using CM5 as a platform, Toshiba is demonstrating a brand-new MMIO accessible Persistent Memory Region (PMR) which enables customers to evaluate the use of 2GB10 of power-loss protected DRAM per drive. Lastly, CM5 boasts an exceptional IOPS per Watt ratio, resulting in operating and cooling savings for the end-user.

Metric CM5 1x4
SR - MB/s11 3,355
SW - MB/s12 2,726
RR - IOPS13 800,000
RW – IOPS14 240,000

Still unsure of which path to take? Toshiba can help! Come see us at booth #407 at Flash Memory Summit and we’ll tell you all about SAS, PCIe, and our newest generation of 64-layer 3D TLC BiCS FLASH enterprise drives.

 


1 PCIe® and PCI EXPRESS® are registered trademarks of PCI-SIG

2 NVMe is a trademark of NVM Express, Inc.

3 MultiLink SAS is a trademark of the SCSI Trade Association

4 Based on MTBF statistical values. MTBF (Mean Time Between Failure) is not a guarantee or estimate of product life; it is a statistical value related to mean failure rates for a large number of products which may not accurately reflect actual operation. Actual operating life of the product may not resemble the MTBF.

5 PM5 10DWPD 3200GB, sustained Multi-Link performance, queue depth 32, 64KiB aligned transfers, 100% entropy

6 PM5 10DWPD 3200GB, sustained Multi-Link performance, 18W, queue depth 32, 64KiB aligned transfers, 100% entropy

7 PM5 10DWPD 3200GB, sustained Multi-Link performance, queue depth 32, 4KiB aligned transfers, 100% entropy

8 IOPS: Input Output Per Second (or the number of I/O operations per second)

9 PM5 10DWPD 3200GB, sustained Multi-Link performance, 18W, queue depth 32, 4KiB aligned transfers, 100% entropy

10 Definition of capacity: Toshiba defines a megabyte (MB) as 1,000,000 bytes, a gigabyte (GB) as 1,000,000,000 bytes and a terabyte (TB) as 1,000,000,000,000 bytes. A computer operating system, however, reports storage capacity using powers of 2 for the definition of 1GB = 230 = 1,073,741,824 bytes and therefore shows less storage capacity. Available storage capacity (including examples of various media files) will vary based on file size, formatting, settings, software and operating system, such as Microsoft Operating System and/or pre-installed software applications, or media content. Actual formatted capacity may vary.

11 CM5 1DWPD 3840GB, sustained x4 performance, queue depth 128, 128KiB aligned transfers, 100% entropy

12 CM5 1DWPD 3840GB, sustained x4 performance, queue depth 128, 128KiB aligned transfers, 100% entropy

13 CM5 1DWPD 3840GB, sustained x4 performance, queue depth 128, 4KiB aligned transfers, 100% entropy

14 CM5 3DWPD 3200GB, sustained x4 performance, queue depth 128, 4KiB aligned transfers, 100% entropy

Disclaimer
The views and opinions expressed in this blog are those of the author(s) and do not necessarily reflect those of Toshiba Memory America, Inc.

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