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Seagate Momentus XT Hybrid Drive
Written by Scott Harness   
Monday, 24 May 2010 00:00

bare_magic_trans_backgrnd-vl550Seagate Momentus XT Hybrid Drive

Seagate have been putting drives in the tech blender again. Did they make a smoothie or or this Hybrid drive still a little lumpy?


SSD's are the current performance item on many PC users wish list, as they do provide an exceptionally fast computing experience. After using mechanical drives, even the fastest mechanical drives, they still pale in comparison to the speeds offered by SSD's. It's great to see your applications load up truly after a double click, and not having to wait around for your system to boot is also a big bonus.

The downside of course is the cost per gigabyte which is pretty high. Your average 256GB SSD is going to cost you around $650, if not more, so for many an SSD is bought with much lower capacity and becomes a boot/applications drive. If you have a laptop, this often makes SSD costs quite prohibitive as to get any sort of decent capacity is going to require you to spend as much as the laptop itself just for storage, if not more.

The however is an SSHD or Solid State Hybrid Drive that features a combination of a 4GB NAND Flash SSD with a high capacity 7200RPM mechanical portion to provide a best of both worlds approach to cheap large storage with high performance. The is the first completely independent SSHD so let's take a closer look shall we?


100.35 x 69.85 x 9.5mm
Power (W)
Seek 1.554, Idle 0.8
Operating 350 2ms, Nonoperating 1000 1ms
500GB (available in 250,320 and 500)
Flash Capacity
Flash Type
Nand SLC (Single-Layer)
SATA 3Gb/s with NCQ
5 years

• Solid state hybrid drive delivers SSD-like performance with hard drive capacity options.
• Adaptive Memory™ technology customizes performance by aligning to user needs for overall improved system response.
• 80 percent faster performance than traditional 7200-RPM drives in PCMark Vantage benchmark scores
• Low heat and vibration—quiet operation without giving up storage capacity and affordability
• OS- and application-independent—designed for any SATA standard laptop PC
• Seagate® 5-Year Limited Warranty

The drive we have for testing today is a 500GB capacity version but Seagate have 250GB and 320GB drives as well, all in the 2.5” format. The mechanical portion of the drive sports a 32 MB Cache and runs at 7200RPM. The drive runs on the SATA 3Gb/s interface and also supports NCQ (Native Command Queuing). The SSD part uses 4GB of SLC NAND Flash. Unlike most larger capacity SSD's on the market today, Seagate have used SLC (Single-Layer) Flash over MMC (Multi-Layer), which should provide a longer life span even with heavy duty use and more efficient throughput, especially when it comes to writes. This longer lifespan probably goes some way to Seagate offering a large 5yr warranty on the Momentus XT.


To make it clear here, the system won't see two separate drives; as far as the system is concerned, there is a single drive. The Seagate Momentus XT is the first ever Independent Hybrid drive (unlike previous Hybrid drives), which makes it compatible with any OS and system you would use a regular SATA hard drive with; no drivers or extra software are required. All you require is a standard SATA 3GB/s interface like any other SATA drive on the market. And yes, it can function in a RAID array as well. This is Seagate's second attempt at a Hybrid drive, but the first attempt didn't fare so well as it relied heavily on Windows Vista being the brains of the operation.

The Momentus XT works by using what Seagate have dubbed Adaptive Memory to learn and anticipate the data you require. The data is first of all written to the mechanical part of the drive, just like a regular drive. Seagate have also included a healthy 32MB Cache for the mechanical portion, so write speeds should be very good too, an area that typically an SSD doesn't do as well in. Over time, the Adaptive Memory uses intelligent algorithms to identify the most commonly used data and this data is then mirrored on the 4GB Flash memory of the drive to provide you with optimal performance in real time. The Adaptive Memory constantly monitors your application and data usage and identifies patterns based on this usage. The applications and certain data are then mirrored onto the faster SLC NAND Flash portion of the drive. This gives you dynamically improved response times that are tailored to each individual end users own personal usage habits. Since the drive is constantly monitoring your usage patterns and anticipating your needs, you can be a professional by day and a gamer at night with the benefits of the extra speed in both scenarios. Everyone has their own unique way of using a PC and the data stored on it, so while there is going to be a certain amount of constant qualifying data that will be cached on the 4GB flash, the drives monitoring of your data means it should always be ready with the data you need or able to learn for the next time even if you're usage changes. As an aside here, should the Flash fail for some reason, the data is still on the mechanical part of the drive, as the data is mirrored as opposed to moved.

The downside here is that you won't get instant benefits because the Adaptive Memory has to learn from your usage patterns first. However, use the same data just two or three times, perhaps by running a program often, then the Adaptive Memory will pick up on this usage pattern and mirror the files to flash. In effect, the Momentus XT will get faster over time as it learns your individual usage patterns, and it can then anticipate the same data you require in the future.


Seagate's main aim with the Momentus XT is to take from both technologies (High Speed Flash and High Capacity Mechanical drives) and provide a drive that gives you near to real world SSD speeds but at only one fourth the price of your average SSD (assuming similar capacities). Seagate are under no illusions that the Momentus XT will compete with an SSD for performance, but they hope that in real world usage it will be a very close experience, and without the hit on your wallet. Since the Momentus XT acts like a regular independent drive, no extra software is required, so no extra costs for anyone there. And because it's a 2.5” drive, you don't have to decide between a high capacity mechanical drive or a high performance SSD for your single drive Notebook. Some Notebooks get around this problem by providing a flash cache module or drive separate to the main mechanical drive, but with the Momentus XT this is unnecessary. Prices should be around the $156 area for a 500GB Momentus XT. That's a hell of a difference compared to a $1000+ 500GB SSD. A 320GB Momentus XT will be $132 MSRP, compare that to the 300GB Velociraptor at around the $210 mark, and again the Momentus looks good. In-fact, pre-orders for the drive show prices that are lower than the suggested MSRP. This does of course make the Momentus XT more expensive than a regular 2.5” drive but if the drive works as Seagate have said, the extra performance will easily offset that cost. There is no impact on noise levels or power usage compared to a regular 7200 rpm 2.5” drive either.

This Momentus XT is clearly aimed at the High Performance market segment, Workstation Professionals, Gamers, Power End Users that can't afford or don't want to pay the high price of an SSD. Like an SSD, it'll fit in well with high end Notebooks and SFF PC's, but since it sports a regular SATA interface and has desktop level performance features, there is no reason not to use a Momentus XT in your desktop.

Many will no doubt turn their noses up at the paltry 4GB of flash provided, but the idea here is to provide a drive that doesn't cost too much more than a regular mechanical drive but provide some of the performance you want from an SSD. If you're a speed junkie, then you're not going to be persuaded by the Momentus XT and clearly an SSD is in your future, but if you don't want to pay out a huge amount for limited capacities (or can't afford it) or don't want to choose between speed and capacity for your single drive system such as a notebook, then the Momentus XT looks to be what you are after. Let's find out shall we?


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