Random Write Speed

The VelociRaptor's two primary strengths are its 2.5" platter size and 10,000 RPM spindle speed. The combination of the two delivers some of the best random access times you can get from a mechanical hard drive, at least one aimed at the desktop. Indeed we see a tangible performance advantage not only over the latest 3.5" hard drives, but also the previous generation VR. The advantage of the NAND equipped Seagate Momentus XT is just as large.

Iometer - 4KB Random Write (QD=3, 8GB LBA)

Obviously even the most affordable SSDs deliver better random IO performance compared to the VelociRaptor as you can see by looking at Intel's SSD 320 here:

Iometer - 4KB Random Write (QD=3, 8GB LBA)

The new VelociRaptor manages a 35% increase in 4KB random write performance over its predecessor, and more than double the performance of Seagate's 7200RPM Barracuda XT. Unlike SSDs, random read and write performance is symmetric on most hard drives so we only really need to look at a single value here. Intel's SSD controllers have typically offered very high random IO performance, so the SSD advantage here isn't unusual.

Ultimately it's this 21x gap in random IO performance that really contributes to why SSDs feel so much faster than mechanical drives. Client workloads aren't purely random in nature (which is why we confine our client random write tests to an 8GB LBA space), but sprinkle non-sequential accesses in the middle of otherwise sequential transfers and mechanical disk performance drops significantly. Small file requests while launching an application, updating file tables, writing to logs, are all examples of small, pseudo-random IO that happen in the background, which can make overall HDD performance drop significantly. While it's true that most client workloads don't require the sort of random IO performance a high-end SSD can provide, it's the additional headroom that SSDs offer that allow performance to remain high regardless of what's going on in the background. We can look at this data another way, instead of average data rate let's look at the maximum number of IO operations these drives can service in a single second:

Iometer - 4KB Random Write (QD=3, 8GB LBA) - IOPS

Based on this list, the average hard drive (excluding WD's 10,000 RPM drives) is capable of handling around 275 4KB pseudo-random write operations per second. Clearly that's not sufficient for the majority of client workloads because once you load up full disk encryption, real time virus checking, background email/IM, backup software and go about your normal application usage you always run into IO limited periods where you're waiting on your drive to finish crunching. Upping the spindle speed to 10,000 RPM gives you a bit of a reprieve, more than doubling performance, but that's not always sufficient given the workload.

At the other end of the spectrum we have a stanard 3Gbps SSD, capable of servicing nearly 15,000 4KB write operations per second. No desktop application could be shipped that required this type of IO performance as it would be unusable on any hard drive. The added performance in the case of an SSD doesn't deliver 21x the performance of a VelociRaptor, but it offers enough performance headroom that applications and file accesses will remain as fast as possible regardless of what's going on in the background. SSDs use their headroom to offer a consistent IO experience, regardless of workload.

Sequential Read/Write Speed

Sequential performance is easily improved by increasing platter density, buffer sizes and pushing for more aggressive prefetch in the drive's controller. As a result, the SSD advantage isn't nearly as significant. Furthermore, the new VelociRaptor delivers such a large increase in sequential speed that it's able to approach the performance of 3Gbps SSDs:

Iometer - 128KB Sequential Read

It's because so much of client workloads are sequential in nature that some users don't really feel a dramatic difference in going from a hard drive to an SSD. The only thing I can add is that the users who are constantly frustrated by the speed of their hard drive will be the ones to most appreciate the move to solid state storage. Shifting focus back to the VelociRaptor however, its sequential read speed is quite competitive with mainstream 3Gbps SSDs. Start comparing to 6Gbps drives and the VR is significantly outgunned.

Again, reads and writes don't vary with the VR but compared to the 160GB Intel SSD 320 there's a shift in the standings:

Iometer - 128KB Sequential Write

Again, compared to larger or faster SSDs the VelociRaptor would surely lose, I tried to pick an SSD that was more representative of what you could get on a budget or with an older drive. Either way the gains over other mechanical drives are respectable, the new VR definitely delivers in sequential speeds as far as hard drives are concerned.

Performance Across All LBAs

Although logical block addressing works linearly, hard drives are made up of one or more circular platters. Platters are written from the outside inward in order to maximize performance (you cover more data in a single rotation of an outer track vs an inner track). I used HDTach to characterize the new VelociRaptor's performance across all LBAs:

The inner most tracks on the VelociRaptor are still accessible at 123MB/s - faster than any 3.5" drive we've tested here. One benefit to using 2.5" platters is remarkably consistent performance across all tracks. Average performance across all tracks is 173MB/s.

Introduction AnandTech Storage Bench 2011


View All Comments

  • ltcommanderdata - Monday, April 16, 2012 - link

    I admittedly only did a quick read of the article so I may have missed it, but were there any comments on noise and vibration compared to previous VelociRaptors and other mechanical drives? Reply
  • Sabresiberian - Monday, April 16, 2012 - link

    My Raptors have always been smoother and quieter than other drives. I have 2 of the first-gen 2.5" mounted on the 3.5" form factor heat sink, and I can't even tell they are running, except to see the drive light on the front of the computer flicker (and, of course, the computer is running properly).

  • retrospooty - Monday, April 16, 2012 - link

    I agree with the conclusion... "if I needed to buy a high-performance mechanical hard drive, it's the one I'd pick."

    I always had a raptor until SSD became affordable to me (about the time of the Vertex2's release). With a 120gb Vertex 3 drive currently $139 after $20 rebate at Newegg, why bother?

    Use the SSD as your OS and apps and several of your favorite games and a large cheap HDD for storage, movies MP3's old games, etc - things that don't need fast access. 120gb is plenty big for that. My Vertex3 is set up that way and has 50% space free still. Fast as hell.

    Is so fast it doesn't even allow the Win7 colors to touch on the launch screen. Before the 4 colors swirl and then come together and strobe, its it Windows. sigh...
  • mcnabney - Monday, April 16, 2012 - link

    Anybody know how the multiple drive setups will work under Win8?

    Apparently the Drive Extender from the original Windows Home Server (which was ripped out of the sequel) is part of Windows 8. What kind of control will be available concerning which files go where when using this in Win8?
  • Sufo - Monday, April 16, 2012 - link

    It's irresponsible to recommend the Vertex 3. Reply
  • LB-ID - Monday, April 16, 2012 - link

    It's irresponsible to recommend OCZ products, period. Their strategy of bringing products to market six months early, then using their customers for the validation phase has long since shown its true colors. Combine that with a policy of ridiculing anyone who dares question them has turned me from a customer to running away from anything they produce. Reply
  • dananski - Monday, April 16, 2012 - link

    I have somewhat mixed opinions about Vertex 3's since we upgraded to them at work. Probably about 50% extra cost hidden in the man hours wasted trying to sort out firmware, and we're still not completely BSOD-free. The price has come down and they're fast, but not faster than my problem-free Intel 510.

    But to generalise to all OCZ products is unfair. My reapers are still great after 4 years, and the SSD bugs are partly down to Sandforce.
  • Samus - Monday, April 16, 2012 - link

    LOL, it's irresponsible to recommend ANY OCZ SSD ;) Reply
  • landerf - Monday, April 16, 2012 - link

    Access time? Reply
  • Scott314159 - Monday, April 16, 2012 - link

    I think there is still a role for the raptor in the budget server market where enterprise SSDs are still too expensive. While in the consumer SSD space confidence and longevity are still not where they need to be (any disagreements or counter arguments with references??).

    I will probably use these drives in my next server build...

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