The chasm between HDD and SSD performance has led to a variety of approaches to merge the capacity and economy of HDDs with the low-latency performance of flash storage. Many of these approaches leverage software and hardware in a multitude of caching and tiering schemes, but these approaches invariably result in host overhead, and require management oversight. Seagate has taken a divergent path in developing their Enterprise Performance TurboBoost SSHD (Solid-State Hybrid Drive) models. TurboBoost drives merge the positive aspects of both storage mediums in a holistic manner, and require no host overhead, and absolutely no management oversight.
Initial TurboBoost revisions were released as Turbo SSHD models, but the newest revision has been rolled into Seagate's Enterprise Performance 15K HDD lineup. This reflects that the Turbo SSHD has matured to mainstream status, and the new model is updated with a 12Gb/s SAS connection. The TurboBoost 15K HDDs still spin at 15,000 RPM, but also employ a 32GB eMLC NAND layer to cache hot data. eMLC provides a very durable and fast storage layer, and Seagate's proprietary AMT (Adaptive Memory Technology) algorithms identify hot data at the block level, and promote or evict data from the flash layer accordingly. A copy of the data is also retained on the platters, but hot data is served from the NAND to realize up to a 3x application performance improvement.
The NAND layer also improves performance of the standard multi-segmented 128 DRAM cache, allowing it to be used as write-back cache. This boosts random write performance without wearing the NAND by allowing the drive to coalesce random write activity in the DRAM layer, and then writing it down to the platters. A portion of the eMLC is assigned as SLC to function as a NVC (Non-Volatile Cache). The drive flushes data stored in DRAM to the NVC with back EMF in the event of an unsafe power loss, creating an extra layer of power-loss protection not provided by standard HDDs.
The new TurboBoost models spin at 15,000-RPM, and step up to the 12Gb/s SAS connection. TurboBoost models come in the standard 2.5" form factor in capacities of 300GB and 600GB. TurboBoost is geared for transactional workloads in blade, rack or tower servers, and it works well in both DAS and SAN/NAS environments. The specifications of the TurboBoost models are identical to the standard 15K models, including power consumption rated at 8.7W active and 5.3W idle. The SDR is also identical with 246 to 180 MB/s from outer to inner, which isn't surprising in light of the fact the TurboBoost models only cache random data. A standard average latency of 2.0ms is also identical to regular models, but data served from cache will perform significantly faster.
The Turbo SSHD features a Non-recoverable Read Error Rate of one per 10E16, and a MTBF of two-million hours, or an AFR of 0.44%. 512e and 4Kn models are available. The drive also features an enterprise-standard five-year limited warranty, and self-encrypting and SED FIPS 140-2 models.
Enterprise Performance TurboBoost 15K has the typical features, and expected reliability and durability of standard 15K HDDs, but offers higher performance in transactional workloads. Let's take a closer look at its caching performance.
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- Page 1 [Introduction]
- Page 2 [Exploring Cache Performance]
- Page 3 [Enterprise Performance 15K HDD v5 Internals and Specifications]
- Page 4 [Test System and Methodology]
- Page 5 [Benchmarks - 4k Random Read/Write]
- Page 6 [Benchmarks - 8k Random Read/Write]
- Page 7 [Benchmarks - 128k Sequential Read/Write]
- Page 8 [Benchmarks - Database/OLTP]
- Page 9 [Benchmarks - Email Server]
- Page 10 [Final Thoughts]