Seagate Momentus XT 500GB Hybrid Drive

Full Review

The Seagate Momentus XT 500GB is a "hybrid" hard drive that provides users a middle-ground between SSDs and HDDs with respect to storage capacity, performance, and price. Externally it looks like a normal laptop hard disk, with a 2.5-inch form factor that fits into a standard 9.5mm z-height drive slot and a SATA-2 data interface. Internally it has special qualities that are unusual for a laptop drive, such as a buffer of 32 MB, a spinning speed of 7200rpm, and 4GB of solid state memory.

In daily-usage testing, we found that the Momentus XT came into its own and shone bright.

Wait, did we really just say that there was Solid State memory on a spinning hard disk? Yes indeed. Think of it as an extended buffer, one which can retain data even between reboots. No, you cannot directly address the solid state capacity on it, it is invisible to the user so the software/OS you are using does not matter. The drive’s controller itself makes of it, using what Seagate calls "Adaptive Memory" to take frequently used files/data from the spinning part and put it on the solid state section of 4GB. The drive is designed to boost read performance, but it will also help write performance.

Until now, storage technology was divided into two camps. Fast SSDs (Solid State Drives) and relatively slower traditional HDDs (spinning magnetic drives). Consumers had to contend with mutually exclusive plus points, where SSDs provided lesser storage capacity at a higher price, and HDDs provided more storage capacity at a lower price. Samsung and Seagate did try the concept of hybrid drives a couple of years ago, but the result was not pretty back then. The problems may have been because of requiring Operating System support, having just 256MB of flash memory or the fact that SSDs had not acquired mass appeal and dropped sufficiently in price.

This newer second-gen drive mixes a bit of solid state with a lot of normal hard disk tech. The 4GB of solid state memory is Flash-NAND, the same type you are accustomed to seeing in pendrives and SSDs, except that it is of the SLC type (Single Layer Cell) to maximize speed. It uses two spinning disk platters to achieve its areal density. Seagate claims power usage averages of 0.8W at idle and 2.2W during normal read/write operation, which places it better than a standard desktop HDD (3.5-inch) which would consume 6W on average. The Momentus XT 500GB capacity drive offers a usable data storage space of 465.76 GB after being formatted, which is on expected lines. All through intense testing, it did not become audible nor did it go beyond getting slightly warm to the touch, both of which are good signs.

Performance
Improved specs and engineering can sound great on paper, but does the Momentus XT truly deliver a measurable performance boost over its standard hard-disk cousins? Let us see if Seagate gets second-time lucky with the Momentus XT series of hybrid drives. We ran the drive through a comprehensive set of tests in the PC World Test Center, on a high-end testbench to eliminate bottlenecks. This included synthetic benchmarks, real world tests and subjective “daily usage” testing as well.

Due to the architecture of the drive, Seagate warned us that we shouldn't expect to see the maximum benefits of flash integration on the first few test passes (we typically run three timed passes for every test we perform). Instead, the Momentus XT would show its true performance colors, consistently, at between passes four through six. So we ran all tests seven times to capture optimal performance. As Seagate indicated, not until pass number three did the drive begin to show stable, consistent results. Also note that traditional testing apps only check the raw speed of the drive itself which overlooks the "hybrid-ness" of the drive, so look at our daily usage tests to find out the actual subjective speed you’d see when using it full-time.

In synthetic tests, we measured a read speed average of 90.5 MB/s, and a write speed average of 89.6 MB/s with a CPU usage of 1 per cent. Read and write access times averaged 16.1 ms and 6.23 ms (milli-seconds) respectively. It was interesting that some tests detected an access time (also called seek time) of only 0.2 ms, a number that ranks up there beside SSDs. We suspect this is because of the integrated 4GB flash onboard, the factor that makes drive a hybrid one. On our PC WorldBench 6 tests, the system with the hybrid drive scored 146, which is comparable to other 7200rpm laptop drives; normal desktop drives and SSDs turn in 2 and 9 points extra, respectively.

Real world tests were conducted when the drive was empty, using a RAMdisk to transcend the speed/access-time limits of any SSD/HDD and to log performance numbers that are not bottlenecked by anything. File read/write speeds stood at 93.78 MB/s and 84.95 MB/s respectively for a single large file (6.42 GB). It fell as expected to 65.21 MB/s and 60.8 MB/s for read and write speed respectively, when copying multiple smaller files (1287 files totaling up to 2.33 GB). Transferring these small files from the first partition to a second one on the same drive (simultaneous read/write) was at a lower speed of 33 MB/s which was expected because the speed chart naturally dips as it approaches the end of the “partition table”. These numbers peg the drive’s performance at a slightly higher level than other 7200rpm laptop hard disks.

In daily-usage testing, we found that the Momentus XT came into its own and shone bright. We ran Windows 7 x64 boot-up tests, as measured after the BIOS POST and until the login screen appeared. This drive almost halved the boot-up time (21 seconds) in comparison to normal desktop HDD that took 38 seconds and 7200rpm laptop HDDs that took 45 seconds. We automated the immediate loading of ten applications after logging in (ranging the gamut of IM, productivity, email client, web browser, and image editor). By the third and fourth time, these apps loaded well and truly fast, leaving the system free for usage right away. Compared to the usual experience where a lot of disk access is ongoing and you need to wait 2 minutes for everything to load and for the system to be usable, the near-zero waiting time is superb.

Since the benefits are mostly on the data read side, think of it as a more advanced version of Pre-fetching. Data that has not been accessed previously won’t benefit from the speed of course. So activities like antivirus scanning and file moving are carried out like a normal drive. When you do frequently access files and applications, they are placed in the solid state area of the drive to benefit from speed. If you use other large files/apps and then come back to the initial set, the initial set would have been knocked out and will have to be loaded from the spinning platters again. If you deal largely with the same set of data repeatedly, the drive is free to reduce power usage on the spinning platters, thus conserving power.

You can call it SSD-like to that extent. But when writing data, the solid state memory is largely by-passed, so you see higher write access times. If you deal with many large files continuously, the solid state memory’s benefits again go unnoticed. That could be the reason Seagate launched a laptop version of a hybrid drive and not a desktop version. The raw performance of RAID0 arrays cannot be used on laptops, so this is a better solution. The work-pattern of most laptop users would benefit from the techniques used by the Momentus XT. Some desktop PC users might consider using this drive as well, for its benefits. It would be interesting to see what the other biggies of the HDD industry do, now that a hybrid drive is proven to perform well.

However, the fact is that the Seagate Momentus XT 500GB is simply a fast laptop hard disk, better than normal ones. Its raw performance is beaten by normal 3.5-inch desktop drives (such as Seagate’s own Barracuda 7200.12 series), higher-end drives such as the WD VelociRaptor, and of course, SSDs. Though clichéd, it is difficult to not draw an automobile parallel. Are Hybrid-fuel cars good? Yes. Are they a good purchase for everyone? Perhaps not, for a lot of reasons including price. The Momentus XT hybrid drive in India is available in capacities of 250GB, 320GB and 500GB priced at Rs. 6,800, Rs. 7,400 and Rs. 8,100 respectively. Seagate offers a warranty of 5 years upon this drive.

Bottom Line

Seagate's Momentus XT hybrid hard drive adds flash storage to increase speed significantly over a standard hard drive in some scenarios. If you want a performance boost on a budget, and you value capacity too, this second-gen hybrid drive makes a good compromise. The Seagate Momentus XT won't give you nearly the same speed boost as an SSD, but it will definitely improve upon what you'd get with a standard 5400-rpm laptop hard drive.