Seagate Momentus XT Hybrid hard disk

Seagate Momentus XT – Ferrari of the consumer disk

Solid State Disks (SSDs) are low capacity storage devices typically used in enterprise storage systems for extremely high performance and low power consumption. Despite its superior IOPS (I/O per second) performance (upto 100X as compared to an enterprise 15K RPM FC disk), it was rarely deployed in enterprises until recent years where technological advances helped to reduce the cost of SSD considerably.

SSDs today are usually built on non-volatile NAND flash memory and flash are available as Single-Level Cell (SLC) or Multi-Level Cell (MLC). SLC flash is typically used in enterprise grade SSDs for its speed and longevity. MLC flash, on the other hand, is slower but has larger capacity. Seagate Momentus XT uses SLC NAND flash.

Features MLC SLC
Bits per cell 2 1
Erase/Write cycles < 10,000 < 100,000
Read Service Time.
Lower is better
50µs 25µs
Write Service Time.
Lower is better
900µs 300µs

So what exactly is Seagate Momentus XT hybrid disk? Think of it as a fusion of the super fast Solid State Disk (SSD) and the traditional SATA hard disk. In this case, Momentus XT will automatically caches the data to the on-board 4GB Read-Only SLC flash so that when the application requests for its data, it will be served out from the flash. In the event that the requested is not available in the flash, Momentus XT will fetch the data from the traditional SATA disk. Hence the trick here is really to have a relatively consistent “pattern” in the usage of the computer so that adaptive memory technology of Momentus XT is able to pre-fetch the data and hence increases the probability of the data being served from the flash, rather than the disk.

Does this sound too good to be true? Is the future really here? Well, at least the reviews on this product seem to indicate that this drive is worth the extra bucks. Since I ran out of capacity on my macbook pro and needed to upgrade the disk, I have decided to give this disk a try.

I did some tests on the time it takes to boot up my macbook pro with the original 5400 RPM disk versus the new Momentus XT and here’s a summary of the results.


With Original HDD 5400RPM With XT Clean Install/No Apps With XT Clean Install and Apps
Run #1 65s 35s 26
Run #2 62s 34s 26
Run #3 60s 34s 26
Average 62s 34s 26s
Time taken to cold boot my macbook pro

As you can see, the performance of this disk is quite amazing. The boot up time of my macbook pro has reduced from 62s to 26s. Is this worth the extra bucks? Well, I think so. 😉

Specifications of the Seagate Momentus XT

  • 2.5-inch laptop PC hard drive
  • 500GB 7200 rpm of spindle speed with 32MB of drive-level cache
  • 4GB of solid state SLC (Single-Level Cell) NAND flash storage

List of applications installed on my macbook pro for the tests

  1. Mac OS X (10.6.8)
  2. Microsoft Office 2011
  3. VMware Fusion 3
  4. Firefox
  5. Adobe CS4
  6. Evernote
  7. Filezilla
  8. Textwrangler
  9. MAMP
  10. Skype
  11. Cisco VPN
  12. Sync-Mate
  13. MacFuse
  14. NTFS-3G
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