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| Introduction and Specifications | ||||
Seagate’s first Momentus XT hybrid drive arrived about a year and a half ago. The original drive featured a 500GB hard drive paired to 4GB of SLC NAND flash and a SATA 3.0 interface. At the time of its release, the original Momentus XT turned out to be a rather compelling product. Its price was relatively low and Seagate’s adaptive memory technology “just worked”, which resulted in increased performance that was seamless to the end-user, regardless of the OS being used.
Although Seagate hasn’t revealed all of the secret-sauce that makes the Momentus XT unique in the current market, understanding how the drive works is fairly straightforward. The 8GB of SLC NAND flash is used as a high-speed repository of sorts. The controller on the Momentus XT monitors usage patterns and copies the most frequently accessed bits of data from the hard drive to the solid state storage. And it all happens independent of the OS or drivers. According to Seagate, the data on the hard drives has to be accessed multiple times before it is copied to the solid state storage and the contents of the flash memory will dynamically and constantly change over time, based on usage. To put it simply, the most commonly accessed data on the platters gets copied to the much higher performing, SLC Flash memory, which results in a performance boost. And it’s not necessarily full files being copied, but rather the most frequently accessed bits of data. We should also point out that a new feature to the updated Momentus XT called Fast Boot uses a small portion of the solid state cache for data used during the boot process, which resides in a special location and won't change often, in order to maintain quick boot times. Knowing how the adaptive memory on the Momentus XT works, reveals one of the drawbacks of a hybrid design such as this one—the flash memory will offer no performance benefit to infrequently accessed or new data. So, with large file copies, application installations, and the like, the Momentus XT will perform like a standard HD. |
| Test Setup and ATTO | ||||||||||||
Our Test Methodologies: Under each test condition, the drives tested here were installed as secondary volumes in our testbed, with a standard spinning hard disk for the OS and benchmark installations. Out testbed's motherboard was updated with the latest BIOS available as of press time and AHCI mode was enabled. Windows firewall, automatic updates and screen savers were all disabled before testing. In all test runs, we rebooted the system and waited several minutes for drive activity to settle before invoking a test.
ATTO is a "quick and dirty" type of disk benchmark that measures transfer speeds across a specific volume length. It measures raw transfer rates for both reads and writes and graphs them out in an easily interpreted chart. We chose .5kb through 8192kb transfer sizes and a queue depth of 6 over a total max volume length of 256MB. ATTO's workloads are sequential in nature and measure raw bandwidth, rather than I/O response time, access latency, etc. This test was performed on blank, formatted drives with default NTFS partitions in Windows 7 x64.
Please note, the ATTO benchmark will not show the benefit of Seagate's adaptive memory technology. Rather, this benchmark shows somewhat of a worst-case scenario where the Momentus XT is limited in performance by its spinning hard disk platters. |
| CrystalDiskMark Benchmarks | ||||
CrystalDiskMark is a synthetic benchmark that tests both sequential and random small and mid-sized file transfers. It provides a quick look at best and worst case scenarios with regard to SSD performance, best case being larger sequential transfers and worse case being small, random transfers.
Like the ATTO benchmarks on the previous page, CrystalDiskMark DOES NOT benefit from Seagate's adaptive memory technology and characterizes only the performance of the Momentus XT's hard drive. |
| PCMark 7 Storage Benchmarks | ||||
We really like PCMark 7's Secondary Storage benchmark module for its pseudo real-world application measurement approach to testing. PCMark 7 offers a trace-based measurement of system response times under various scripted workloads of traditional client / desktop system operation. From simple application start-up performance, to data streaming from a drive in a game engine, and video editing with Windows Movie Maker, we feel more comfortable that these tests reasonably illustrate the performance profile of SSDs in an end-user / consumer PC usage model, more so than a purely synthetic transfer test.
PCMark 7's storage benchmark, due to its psuedo-real-world workloads, does show the benefits of Seagate's adaptive memory technology. We ran this test three times to illustrate how the Momentus XT's performance scales from run to run as its solid state cache comes into play. The test was run multiple times on the other hybrid solutions as well, and the results from their third runs are reported here. The other hybrid solutions, however, offered somewhat better performance in most of the tests. As you can see, the Momentus XT's performance scales significantly as its solid state cache is utilized and the drive offers performance much better than a standard 7200RPM hard drive. |
| Our Summary and Conclusion | ||||
Performance Summary: The Seagate Momentus XT 750GB drive performed relatively well throughout our battery of tests. When its solid state cache comes into play, the Momentus XT is clearly faster than a standard hard drive and in some instances offers true “SSD-like” performance. The updated Momentus XT is also clearly faster than the first-gen drive due to its faster HD, increased solid-state cache and tweaked adaptive memory algorithms that react more quickly than the original’s. In comparison to other hybrid solutions, the Momentus XT competes favorably, but Intel’s Smart Response technology or options like the RevoDrive Hybrid are ultimately faster—sometimes much faster. Finally, compared to a standalone SSD, the Momentus XT trails in every facet of performance.
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When we first took a look at the original Momentus XT mid-last year, we stated in our conclusion that, “While the Seagate Momentus XT doesn't clearly dominate all standard hard drives across every type of usage model, Seagate's hybrid implementation seems to address its intended markets quite well.” That statement is also true today, and the updated drive is definitely superior to the original in virtually every way. However, the storage landscape has changed dramatically since the original drive was released.
