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3.5” Test HDDs: Hitachi Ultrastar 15K450, 15K600

3.5'' Vs. 2.5'' SAS HDDs: In Storage, Size Matters
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Hitachi Ultrastar 15K450

The Ultrastar 15K450 is no longer Hitachi's most current model, as it was replaced by the Ultrastar 15K600 a few months ago. We decided to include it, though, because the 450GB generation has been deployed in large quantities by all hard drive makers, and it's closest to the 147GB, 15,000 RPM drive we used for data density comparison.

Hitachi offers 300GB and 450GB capacity points and utilizes a SAS 3Gb/s interface along with 16MB of cache memory. The 450GB flagship is based on four platters; only three are required for 300GB. Smaller capacities are not available. Power requirements at idle for the 15K450 are lower than on the 15K600, but slightly higher under load.

The 450GB drive is also the hottest of the three, showing why differences between one product generation and the next can be significant. Let’s move on to the current 600GB drive.

Hitachi Ultrastar 15K600

The Ultrastar 15K600 is Hitachi’s top model, available in 300, 450, and 600GB capacities. Once again, it takes four platters to reach the top capacity, while the other two models come with two and three platters. We utilized the 600GB unit in our tests.

Hitachi quadrupled the cache capacity from 16MB to 64MB, and it ugraded the SAS interface from 3 Gb/s to 6 Gb/s. This doesn’t have a direct impact on performance, as the drive's platter I/O throughput is physically limited to a maximum of 195 MB/s. However, SAS 6Gb/s allows for higher peak performance into and off the cache memory, and it's utilized to connect storage applications to host adapters.

The drive requires a bit more power than the 450GB predecessor when it idles, but it's better under load. Since performance increases quite a bit compared to the Ultrastar 15K450, power efficiency both for I/O performance per watt, as well as throughput per watt, makes impressive steps forward. However, the 2.5” drive still does much better.

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  • -2 Hide
    steddy , May 8, 2010 3:44 PM
    If the 3.5 inch drives have twice the number of platters as the 2.5 inch drives, shouldn't their performance be similar to that of two 2.5 inch drives in RAID? Or does the performance of multiple platters not scale that way?
  • -1 Hide
    Anonymous , May 8, 2010 11:31 PM
    Nice article.

    "Two 2.5” SAS drives in RAID will outperform one fast 3.5” SAS drive in every workload."

    I would like to see proof of this, as I don't believe the "in every workload" bit. RAID-0 and -5 don't always deliver performance as promised. As far as I know, it depends on the file sizes, among other factors. Applications that use thousands of little files (web servers come to mind) can't always get a good performance boost from data striping, as the overhead required to read/write many small files outweighs the speed gains achieved by spreading the load across multiple drives. In this case, one faster 3.5" drive might outperform two slower 2.5" drives.
  • 1 Hide
    Alvin Smith , May 9, 2010 2:56 AM

    SO ... We ALL DO have 5.25" drive bays as a common option ... Can you guess what I am gonna say next ??

    Perhaps mechanical drive manufactureres should revisit the 5.25" form-factor for super-perpendicular, ultra-dense, high-performance desktop apps, such as video editing and graphics (and other HD+ media content apps).

    UltraRaptor 5"x10K dual-platter short-stroked.

    = or not =
  • -1 Hide
    paperfox , May 10, 2010 5:07 AM
    lol, Alvin you beat me to it
    Ive always wondered what if the latest hard drive technology was applied to the old 5.25 standard. I can easily see 300 MB/s transfer speeds and at least 1 TB platters with enough room for maybe 6 or so in one drive. Although realistically the price per gigabyte would be unmatched and the price per performance and efficiency would be hideously low compared to the trend I see on page 8... unless you add another actuator arm :)  but thats a whole other article.
  • 0 Hide
    distortion , May 11, 2010 12:33 AM
    try spinning a stack of 5.25" disks at 10k rpm.
  • 1 Hide
    davidb77380 , May 12, 2010 2:08 PM
    "2.5” and 3.5” enterprise drives are based on the same platter diameter"
    LMAO ...another drive "expert" who doesn't know ____ from shinola.
  • 1 Hide
    GullLars , May 16, 2010 11:15 AM
    @Alvin Smith: I'm more interrested in high-density low-RPM 5,25" drives for desktops and fileservers. I would easily buy sine 10TB 5,25" 3600RPM (or 1800RPM?) drives for RAID-5 to store huge ammounts of media and other files. Given the price pr GB was right ofc. 50MB/s sequential read/write pr drive would be sufficient for mass storage.
  • 0 Hide
    Anonymous , June 4, 2010 12:11 PM
    " Two 2.5” SAS drives in RAID will outperform one fast 3.5” SAS drive in every workload"

    ...and what about a drive failure in your striped array? You should consider the whole, bigger picture, not just speed and capacity.
  • 0 Hide
    sohelm , April 6, 2013 10:38 PM
    WHICH ONE IS BATTER 2.5” SAS OR 3.5” SAS