Seagate hybrid drive delivers SSD performance at HDD price

After failing to gain market traction with its first iteration of hybrid drives three years ago, Seagate today announced a new hard-disk and solid-state combination drive with as much as 500GB of capacity, but with a 250GB model starting at $113.

While Seagate's last attempt to market a hybrid drive focused on energy savings, its new Momentus XT is all about performance and capacity.

The drive has special software that tracks a person's use trends and then uses the SSD component of the drive to optimize performance, and it can adjust that performance over time with changes in user behavior.

The Momentus XT is a 7200-rpm serial ATA (SATA) hard-disk drive combined with 4GB of SSD capacity and 32MB of DDR3 cache memory. Seagate was unable to offer read, write speeds on the drive.

The combination, Seagate said, blows by traditional 7,200-rpm and 10,000-rpm hard-disk drives for read and write speeds, and nearly matches pure-SSD performance for the same.

"We heard loud and clear from our user's feedback back [on our last hybrid drive] that our next drive had better be a high performance one," said Mark Wojtasiak, senior product marketing manager at Seagate.

Seagate said it tested the Momentus XT against three other industry-leading drives, included a pure-SSD, a 10,000-rpmWestern Digital Velociraptor hard drive, and its own 7200-rpm Momentus hard-disk drive. It used ASUS G51-series gaming notebooks running Windows 7 Home Premium, running identical scripts on each.

"We booted within 5 seconds of an SSDs boot time, and we were 15 seconds faster than a 300GB Velociraptor and 36 seconds faster than our 7200-rpm [Momentus] drive," Wojtasiak said.

When it came to loading applications, the Seagate Momentus XT was within range of a SSD drive, and it was "significantly" faster than the Velociraptor or Momentus hard drives, he said.

In the fall of 2007, Seagate launched its first and only hybrid drive, the Momentus 5400 PSD, or Power Savings Drive. The 2.5-in. PSD had a spindle speed of 5,400 rpm and only 256MB NAND flash capacity. That drive failed to sell well.

The purpose of the PSD's SSD component was to act as a type of cache so that boot times would be improved and the hard drive platters would only spin up about 10% of the time, consuming up to 50% less power than traditional 5400-rpm spinning drives. But the drive offered little capacity compared with hard-disk drives of its day, and performance was only modestly better.

Stephen Baker, vice president of computer hardware industry analysis at research firm NPD Group, said, "I think they've tried to address some of the issues around price, and they've tried to address the fact that pure SSD drives are pretty expensive, and hybrids in the past didn't offer you a lot of value -- they didn't perform mush better than SSDs, but they cost much more."

Baker said from a price-point perspective, the Momentus XT is very competitive with hard drives and SSDs. For example, an Intel X25-M (consumer-class) SSD with 80GB of capacity costs about $215 on online retail sites such as

The new Momentus XT comes in 250GB, 320GB and 500GB capacities and has a manufacturer's suggested retail price of $113, $132, and $156, respectively. ASUS said it will be the first PC maker to ship systems featuring Seagate's Momentus XT drive.

The drive is targeted at PC gamers, work groups, or developers and other computer enthusiasts who want to build their own high-performance computer. If it catches on, eventually, the product is expected to be marketed at the general laptop computer market, Wojtasiak said.

Secret sauce

Along with the Momentus XT, Seagate announced its Adaptive Memory software, an algorithm that maps user patterns and optimizes the drive's performance based on those patterns.

Wojtasiak said the first time a user boots a system with the Momentum XT drive, the Adaptive Memory kicks in and begins learning use patters, booting the OS and then the most frequently used applications first.

By second boot, the system knows about 80% of a users system preferences and habits, and by the third boot, the drive's performance optimization peaks and remains topped out, he said.

The Momentus XT also performs the same regardless of the operating system, Wojtasiak said. "This is operating system and application independent," he said.

According to Seagate, OS independent means that the operating system does not determine what data should be written to flash memory versus the disk platters. Data placement is decided by the Momentum XT's algorithms, which monitor accesses to the disc and identify the data that would see the biggest performance benefit from being be put in flash memory. It also means that the solid state hybrid drive will show a performance benefit when installed in a system with any operating systems: XP, Vista, Windows 7, Linux, Mac, etc.

"I think Seagate has done a good job of acknowledging they have had two pitches that they swung at in this product segment and they missed both," said Mark Geenen, an analyst with research firm Trendfocus.

"With this product, it looks like they've made some good design adjustments so that without a fully optimized OS this product can still learn over time user tendencies and adjust performance," he said.

Geenen said he was impressed with performance demonstrations of the Momentus XT by Seagate. "I think they've made it an attractive product," he said.

A year and a half ago, Seagate announced its first SSD, the 2.5-in Pulsar, an enterprise-class drive that uses single-level cell (SLC) NAND flash chips. The PSD offered up to 240MB/sec. sequential read speeds and 200MB/sec. sequential write speeds or peak performance of up to 30,000 read IOPS and 25,000 write IOPS.

It also claimed the Pulsar was as much as 20% faster than standard 5400-rpm hard drive technology, cuts energy consumption by 50% and improves mean time between failure (MBTF) by 50% compared with traditional drives.

Stuck on SLC SSD

The company has yet to produce a consumer-class SSD using less expensive multi-level cell (MLC) NAND flash chip technology, however.

Like with the Pulsar SSD, Wojtasiak said Seagate stuck with SLD NAND flash for the Momentus XT. SLC NAND flash memory, which stores just one bit per cell, natively has higher performance and vastly better endurance than MLC NAND flash.

SLC typically can sustain 10 times the number of write-erase cycles as MLC NAND flash, even though newer wear-leveling software is helping to even that playing field.

"What's important to note about the SSD is that data is always written to disk first and then mirrored to the flash memory," Wojtasiak said. "So there is no risk of losing that data should something happen to the flash."

In its own tests, Seagate said it emulated writing 250GB of data to the Momentum XT over a five-year span, and "saw very little to no SSD degredation."

The Momentus XT uses USB 3.0 interconnect with up to 4.8 Gbit/sec. throughput and native command queuing (NCQ), and also has an eSATA port for use of the drive in an external enclosure.

While Baker was impressed with changes made for the Momentum XT, he said the biggest hurdle facing its uptake is building a market for such a product.

"It's about the value proposition as they try to take over more of the 2.5-in drive market because 2.5-in. drives are not as popular a product as 3.5-in. drives for your specialty users who like to build their own systems," Baker said.

"The key is to develop a culture of buying big and cheap drives for capacity and then supplementing them with products like [the Momentus XT] to boost the performance," he said.

Also today, Seagate announced two new versions of its 5400-rpmand 7200-rpm Momentus traditional hard drive, with up to 750GB of capacity.

Lucas Mearian covers storage, disaster recovery and business continuity, financial services infrastructure and health care IT for Computerworld. Follow Lucas on Twitter at Twitter @lucasmearian or subscribe to Lucas'sRSS feed. His e-mail address is


Copyright © 2010 IDG Communications, Inc.

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