Seagate's Momentus XT Reviewed, Finally a Good Hybrid HDD
by Anand Lal Shimpi on May 24, 2010 9:31 AM EST- Posted in
- Storage
- SSDs
- Seagate
- Momentus XT
- Hybrid Drive
- SSHDs
AnandTech Storage Bench
The first in our benchmark suite is a light usage case. The Windows 7 system is loaded with Firefox, Office 2007 and Adobe Reader among other applications. With Firefox we browse web pages like Facebook, AnandTech, Digg and other sites. Outlook is also running and we use it to check emails, create and send a message with a PDF attachment. Adobe Reader is used to view some PDFs. Excel 2007 is used to create a spreadsheet, graphs and save the document. The same goes for Word 2007. We open and step through a presentation in PowerPoint 2007 received as an email attachment before saving it to the desktop. Finally we watch a bit of a Firefly episode in Windows Media Player 11.
There’s some level of multitasking going on here but it’s not unreasonable by any means. Generally the application tasks proceed linearly, with the exception of things like web browsing which may happen in between one of the other tasks.
The recording is played back on all of our drives here today. Remember that we’re isolating disk performance, all we’re doing is playing back every single disk access that happened in that ~5 minute period of usage. The light workload is composed of 37,501 reads and 20,268 writes. Over 30% of the IOs are 4KB, 11% are 16KB, 22% are 32KB and approximately 13% are 64KB in size. Less than 30% of the operations are absolutely sequential in nature. Average queue depth is 6.09 IOs.
The performance results are reported in average I/O Operations per Second (IOPS):
Under typical multitasking workloads that aren't write intensive, the Momentus XT performs much like the new VelociRaptor. This isn't a typical notebook drive at all. We're still far away from even the cheapest SSDs though.
If there’s a light usage case there’s bound to be a heavy one. In this test we have Microsoft Security Essentials running in the background with real time virus scanning enabled. We also perform a quick scan in the middle of the test. Firefox, Outlook, Excel, Word and Powerpoint are all used the same as they were in the light test. We add Photoshop CS4 to the mix, opening a bunch of 12MP images, editing them, then saving them as highly compressed JPGs for web publishing. Windows 7’s picture viewer is used to view a bunch of pictures on the hard drive. We use 7-zip to create and extract .7z archives. Downloading is also prominently featured in our heavy test; we download large files from the Internet during portions of the benchmark, as well as use uTorrent to grab a couple of torrents. Some of the applications in use are installed during the benchmark, Windows updates are also installed. Towards the end of the test we launch World of Warcraft, play for a few minutes, then delete the folder. This test also takes into account all of the disk accesses that happen while the OS is booting.
The benchmark is 22 minutes long and it consists of 128,895 read operations and 72,411 write operations. Roughly 44% of all IOs were sequential. Approximately 30% of all accesses were 4KB in size, 12% were 16KB in size, 14% were 32KB and 20% were 64KB. Average queue depth was 3.59.
Crank up the sequential writes and you lose the benefit of the 4GB of SLC NAND on board the Momentus XT. It still delivers competitive performance with the X25-V thanks to the latter's limited write speeds, and it is faster than a conventional 2.5" drive as read operations still come off the NAND, but you don't get VelociRaptor performance out of it.
The gaming workload is made up of 75,206 read operations and only 4,592 write operations. Only 20% of the accesses are 4KB in size, nearly 40% are 64KB and 20% are 32KB. A whopping 69% of the IOs are sequential, meaning this is predominantly a sequential read benchmark. The average queue depth is 7.76 IOs.
As a benchmark that's bound by sequential read performance it's not surprising to see the Momentus XT not pull ahead here. Remember that we're limited by how quickly data can be streamed out of a single NAND device so you don't see a huge improvement in performance.
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7Enigma - Tuesday, May 25, 2010 - link
" With So much RAM we could cache those Random Read Write Directly to RAM. Why would we need a Hybrid HDD?"I think what is confusing you is the differences between RAM and Flash. RAM stores data while constantly consuming power. When the power is cut the data is lost. Flash retains the data when power is cut. It is also much slower than RAM in terms of read/write performance (RAM drives have been a geeks dream for a couple years now but the costs are still quite prohibitive. It seemed like we were getting closer to being possible for the average tech geek without a trust fund when RAM prices were so low last year but due to the recent price hikes it's again out of reach).
So to answer your question IMO this drive is designed for a laptop computer where you only have a single HD bay and power consumption is a significant issue. In a laptop situation it is not practical to use RAM as a cache since you'd be draining the battery even when the computer is off.
janus-cassandra - Monday, May 24, 2010 - link
Anand I think you are missing important advantages of and SSD in a laptop, (1) lower power consumption than that of a traditional drive with spinning platters and more importantly (2) decreased susceptibility to catastrophic data loss due to a hard drive crash when one's computer is dropped or undergoes any other rapid acceleration and deceleration. As this last consideration happens all to often with laptops, it seems to me that an SSD drive should be standard issue in most, if not all laptops. A hybrid drive will not provide this protection.johndoe74 - Tuesday, May 25, 2010 - link
you guys should have included a 500 GB 7200 rpm drive in there as well (or instead of the 5400 rpm) for the sake of comparison. a 5400 rpm drive is kind of a dinosaur these daysKlinky1984 - Tuesday, May 25, 2010 - link
Hybrid drives are probably one of the most pointless technologies of the last give years. I don't see how they will ever amount to much. The only way they will is if the cache becomes massive, about the size of what SSDs are now and has a smarter caching algorithm. I can do the same thing that they are doing with their hybrid drive with windows already. Just plop in 8GB of RAM & set windows to prefer system caching. Bam, whatever ram you're not using is used as a cache for reads & that memory can always be reclaimed by programs needing to use it.Hybrid drives only have the negatives of SSD(cost) with the negatives of HDDs(speed, reliability, noise, power consumption), without much of the benefit. Whoever thought "hey, put some flash on it and then we'll let the HDD spin down!', great idea when the hard drive takes probably about 0.5 seconds in good scenario to boot back up, but some could take a couple seconds. Not a good user experience. Boot times look nice, but who spends their time rebooting their computer all day? Is 30 extra seconds booting going to be worth the added cost?
Maybe Seagate should focus efforts on a "dual drive" where you get a 32GB SSD & a 500GB HDD combined into a a single 2.5" form factor. That would let people use the 32GB as their OS drive & the 500GB for their large files, etc.
mpx999 - Tuesday, May 25, 2010 - link
Actually best of high-end disk arrays of today use Flash as a cache. For example NetApp uses module called PAM II which is up to 512MB of SLC used a cachehttp://www.netapp.com/us/products/storage-systems/...
Oracle storage systems, especially 7000 series, also use Flash Caches known as L2ARC i ZIL.
http://sun.systemnews.com/articles/134/4/OpenStora...
So flash cache is a proven technology! They just need to go above 4GB to get better results.
hadifa - Tuesday, May 25, 2010 - link
Normal HDD write speed, and very good read speed the second time for small files.For that purpose, this drive is very good and the 4GB is not that bad because only small files are cached, though I would have hoped for at least double that. There is no mention of how small the file needs to be in order to be cached, or maybe I misunderstood the article.
This drive faces two challenges:
1- Just one NAND chip so no parallel read so limited read speed of about 30-40 GB p/s
2- The NAND is used only for reads, so the write speed is not accelerated.
I'm not going to fuss a lot about the write, but I hope they make a version with say 2*4GB chips and a controller to raid the reads, I would be happy to shell some extra hard earned money for that.
Klinky1984 - Tuesday, May 25, 2010 - link
It's not a "Smart Hybrid" like what was being proposed earlier, with Windows Vista/7 being able to identify it as being a hybrid drive and optimize your experience by placing the most used files into the flash cache. It's as "Dumb Hybrid" essentially the flash is just another layer on top of the normal in-memory buffer. Play a large video file a couple times and all your program files are flushed from the cache, just due to the amount of data going back and forth and since the cache is "dumb" it doesn't know if the sectors it's caching are part of an important document or some image from Temporary Internet Files.It may not be bad if you have small needs, but I think a lot of enthusiasts would be disappointed with it.
zodiacfml - Tuesday, May 25, 2010 - link
I agree with all his comments.This is a good hybrid HDD, but to laptops only since the price premium is $50 to $90 which is quite expensive. For the same price or little more for the desktop, we can buy an SSD and HDD with a lot more performance and capacity.
For his recommendation, this is still a good drive for notebook users looking for more capacity and performance since SSD's, though perfect for the application, is too expensive and lack capacity. Don't doubt the reliability since writes and storage are done on the platters, same reliability with mechanical HDD.
Lastly, I think the 4GB size of SLC NAND flash is chosen as the least (expensive SLC) amount of memory for the most often used files or blocks (typical usage - OS, common Apps). Adding more or making it twice bigger will only benefit users with more and varied apps. It can be done with dual channel but the performance improvement will not be as great. Simply, Seagate just wants more margins and less trouble.
Chloiber - Tuesday, May 25, 2010 - link
4GB is more than enough!On a regular desktop system, you can store ALL files up to 256k on 4GB...and for bigger files, a HDD isn't much slower than a single NAND module.
ABR - Tuesday, May 25, 2010 - link
I hate to burst peoples' bubbles here but how many of the files slowing down boot are going to stay in the 4GB cache? Assuming you spend more of your time running your computer and working with other files that get loaded and unloaded more often than core startup components (somewhat questionable with Windows, I realize ;), then the only time you'll see boot speedup is in artificial tests. Of course, that's the way you should want it...