Seagate's hot-rod hybrid

Seagate's hot-rod hybrid

Summary: A hybrid of SSD and hard drive that gives you the best of both. Does Seagate's new Momentus XT deliver? See for yourself in a couple of short videos in my review.

TOPICS: Storage, Hardware

A hybrid of SSD and hard drive that gives you the best of both worlds. Seagate's new Momentus XT on my 17" unibody MacBook does it. Almost.

Specs Take a standard issue 7200 rpm, 500 GB notebook SATA drive. Add 4 GB of fast and reliable single-level cell (SLC) flash. Make it look like a standard drive to the OS by keeping all the magic internal.

Give it smarts to learn about high-frequency small-block transfers. Put those blocks in the flash and voilà: super-fast small block access; leaving big sequential I/Os to the disk.

For a lot less money!

Theory Disk drives offer cheap capacity and good large read/write (R/W) bandwidth. The R/W bandwidth improves over time as drive capacities grow due to higher bit density.

Flash SSDs offer sub-millisecond access times at a high price: $2-$3/GB. SSD access times are about 150x faster than a notebook hard drive, while R/W bandwidth is only about 2x faster.

Maximum bang for the buck? SSD to store many small files - like DLLs in Windows - to minimize accesses, and let the disk handle the large R/W traffic. Why pay 40x for a 2x performance boost?

Flash capacity? 4 GB can store 4 million 1k files. That saves a lot of access time.

Test An early 2009 17" unibody MacBook Pro with 4 GB RAM and 2.66 GHz Core Duo 2. Swapped the current 7200 rpm, 500 GB Hitachi for a 7200 rpm, 500 GB Momentus XT with 4 GB SLC flash.

For the first test I formatted it with HFS+ using the Mac's Disk Utility. Then I used the excellent Carbon Copy Cloner to clone the system disk to the XT.

Results Boot performance sucked compared to the old drive's ~45 second boot:

  • First boot took 2 minutes 4 seconds
  • Second took 1 minute 19 seconds
  • Third took 1 minute 6 seconds

After consulting with Seagate I did a clean install of OS X. Reformatted the XT, installed Mac OS 10.6 Snow Leopard, migrated accounts and data. Took 3 hours, but the process worked perfectly.

New boot times went to ~45 seconds again. Not what I had hoped - the SSD on my MacBook Air booted in 15-20 seconds - but competitive. Other testers have had better results so Seagate is sending me another drive. I'll update the results later this week.

Application results were much more impressive. Because the drive learns, the first time you bring up an app it happens at disk speed. But the 2nd time!

Mail startup went from 5 seconds to 1.5. Microsoft Word startup went from about 12 seconds to less than 3. See for yourself in this 15 second clip:

And the bigger the app, the bigger the potential speed up. Look at this 1 minute clip of the 1st and

From 45 seconds to 10 17? Way faster than my Mac Pro's 10k system disk.

Note that rarely opened apps won't do as well as the algorithm favors apps that get used more often. Pure SSDs don't have that variability.

Pricing Announcement pricing:

  • 500 GB/$156
  • 320 GB/$122
  • 250 GB/$113

These prices are about double the street prices for the non-hybrid drives. Once Seagate gets some competition they should drop.

The Storage Bits take Looks like a home run for Seagate. The architecture is clean, the performance advantages are real, and pricing is not too bad - especially compared to SSDs.

SSD adoption has stalled because flash prices have firmed up. Few are willing to pay $200-$300 for a smallish SSD in a $700 notebook. But $100? OK.

Seagate could use cheaper MLC flash in 8-16 GB caches without wearing it out. There is every reason to put this in 3.5" drives as well. After all, if the flash does fail all your data is on the hard drive - no loss there.

By blurring the performance difference between disk and SSD, these drives will ensure that hard drives dominate for at least another decade. And they'll put pressure on SSD prices.

But don't count on these showing up in RAID arrays soon. Arrays already have a lot of moving parts and hybrid drives add some subtle wrinkles.

Comments welcome, of course. No money changed hands, but I must say that I'll be reluctant to return the review unit. Update: As a number of commenters pointed out - thanks! - I screwed up: the original video showed a reboot from system cache. When I got the time I reshot the FCP startup after a reboot. It was still 40% of a regular drive and still much faster than a 10k drive on my Mac Pro. Sorry about that! End update.

Topics: Storage, Hardware

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  • Ok.. So what we've got here is a hard drive with ReadyBoost built in...

  • OS independence is a good thing

    Relying on OS vendors for storage improvements is a long hard road. Look at the 10 years it has taken to get 4k sector support.

    This is much cleaner. And it works.

    R Harris
  • File system cache results?

    Could your decreased launch time be the result of the file system cache and not the SSD? I performed the same test you did (opened Word, closed it, opened it immediately) with my Windows XP system and Word 2007. Initial launch took 5 seconds. A second launch took less than 1 second.
    • Confirmed: File system cache.

      I just launched Word 2008 on my MacBook running Tiger. Initial launch was slow. Subsequent launches were fast. My MacBook (or PC I did the initial test on earlier) has no SSD drive.
  • Did you flush the cache each time?

    I don't doubt what you reported but the OS's disk cache produces similar results for me. After a reboot an application takes much longer to load with a 2nd load taking much less time. That's due to the app being stored in DRAM not Flash. Plus once it is cached in Flash you should get the same performance boost AFTER you reboot since it is not volatile.
  • The SLC cycling bothers me.

    How many r/w cycles is the SLC in the drive rated for? I will bet that the SLC Flash will wear out long before the HDD itself. Perhaps you can elaborate on this.
  • The SLC part of this Hybrid concerns me.

    Hi Robin. Since the SLC Flash is solely being used as a cache, the amount of r/w cycles is of great concern to me. What are the MTBF specs for the SLC and HDD components of the Hybrid? I will bet that the SLC will go long before the HDD - in that case what happens to the drive?
  • RE: Seagate's hot-rod hybrid

    hey I;m new here, but this Seagate thing reminded me of something. i checked, and I was right

    Similar philosophy (if not the same) is used in SUN Open Storage where you can combine Read optimized and Write optimised SSD with 7.2k SATA disks, and leave it to storage to do the work.
    I understand that this is on disk level, rather on whole storage level (that consists of disks, server with OpenSolaris with ZFS...), but just noticing.

    Good idea. Lets see where it will take us to.
  • Sounds like's MFT

    Finally, vendors are figuring out how to wring some real performance out of these things.

    Now, how about tackling the power and reliability issues.
  • WHAT THE . . . . 1.7 mins / 1.2 mins / blah blah seconds

    #1 I am not a PC guru but . . . <br>When you're shutting down your PC (not laptop) why can't the basic boot-UP process to the OS loading be actually stored in memory? Will this not save SOME of your precious boot-up time? <br><br>Personally waiting an extra 30 seconds for the OS to load makes me NO difference. <br>CHEEZE-UZ. . . that miniscule amount of time takes what. . . . 4 sips of coffee? <br>Life isnt THAT short people.

    Get that reboot time down to 10 seconds MAYBE you have something there. . .
    . . I said maybe cause SOMEONE will still complain it takes THAT LONG!!!


  • How does this rate with VelociRaptor HDDs and ReadyBoost?

    I would be really interested in any info, tests or what ever regarding this solution (which sounds promising) against a fast spinning (10,000 rpm) HDD, like the VelociRaptor and a fast USB Flash stick used as ReadyBoost?
    I am Gorby
  • Installed Seagate Momentus XT on my 17? unibody MacBook Pro

    Followed the same steps you indicated (Disk Utility format, Carbon Copy Cloner to mirror the disk, swapped drives & booted) but did not experience the boot delays you described. One additional step I performed before copying the drive was a "repair permissions", which I do periodically to maintain good performance. You may want to try doing that on your Mac as well to see if that fixes the boot delay problem