Exploring Performance Consistency in USB 3.0 Flash Drivesby Ganesh T S on November 15, 2014 2:00 PM EST
SSD technology has advanced to a stage where it is possible to have flash drives with bona-fide SSD controllers. The addition of a SATA to USB 3.0 bridge provides an ubiquitous high-speed direct attached storage interface. We have already looked at the Phison S9-based Corsair Flash Voyager GTX and the SandForce SF2281-based Mushkin Ventura Ultra. Our review of the Mushkin Ventura Ultra 120GB drive had a comment about the device's thermal throttling issues. This piqued our interest and we set out to see if any of the other units evaluated before had such issues. Obviously, we were also interested in determining whether our Ventura Ultra sample had the problem. In the case of throttling, we also wanted to make our review complete by bringing out the circumstances under which it would trigger. As we will see further down in this piece, our experiments did find evidence of throttling in the Mushkin Ventura Ultra.
Recently, we also received a sample of another SSD controller-based flash drive. Putting that drive through our throttling test revealed even worse results compared to the Mushkin Ventura Ultra. Upon our feedback, the manufacturer is contemplating a firmware update. In this piece, we will refer to the unit as 'BrandX 240GB' (a complete review of the unit with benchmark numbers will be published once the manufacturer provides us a resolution for the throttling issue). The list of DAS units put under the performance consistency scanner is provided below.
- Mushkin Ventura Ultra 120GB
- BrandX 240GB
- Corsair Voyager GTX 256GB
- LaCie Rugged Thunderbolt 500GB
- Mushkin Atom 64GB
Performance Consistency Evaluation Methodology
Our testing methodology for DAS units takes into consideration the usual use-case for such devices. The most common usage scenario is transfer of large amounts of photos and videos to and from the unit. In order to tackle this, we created three test folders with the following characteristics:
- Photos: 15.6 GB collection of 4320 photos (RAW as well as JPEGs) in 61 sub-folders
- Videos: 16.1 GB collection of 244 videos (MP4 as well as MOVs) in 6 sub-folders
- BR: 10.7 GB Blu-ray folder structure of the IDT Benchmark Blu-ray (the same that we use in our robocopy tests for NAS systems)
These folders were put in a RAM drive on our testbed. Using robocopy, each folder was copied from the RAM drive to the DAS (write benchmark) and back to the RAM drive (read benchmark). This process was repeated thrice. To check for performance consistency, we instrumented our benchmark script to record the flash drive's read and write transfer rates while the robocopy process took place in the background. For supported drives, we also recorded the internal temperature of the drive during the process.
Aspects that may influence performance consistency include thermal throttling and firmware caps on access rates to avoid overheating or other similar scenarios. This aspect is an important one, as the last thing that users want to see when copying over, say, 100 GB of data to the flash drive, is the transfer rate going to USB 2.0 speeds. The graphs below show the speeds observed during our real-world DAS suite processing with the instrumented benchmark script. The first three sets of writes and reads correspond to the photos suite. A small gap (for the transfer of the videos suite from the primary drive to the RAM drive) is followed by three sets for the next data set. Another small RAM-drive transfer gap is followed by three sets for the Blu-ray folder.
An important point to note here is that each of the first three blue and green areas correspond to 15.6 GB of writes and reads respectively. Throttling, if any, is apparent within the processing of the photos suite itself.
The Mushkin Ventura Ultra 120GB does throttle after the S.M.A.R.T temperature report reaches 45 C. In our testbed (ambient at 22C), this temperature was reached after approximately 18 GB of writes and 16 GB of reads without any interruptions. Beyond this, the write speeds got capped around 80 MBps (compared to the non-throttled 100 MBps), while the reads got capped around 100 MBps (compared to the non-throttled 140 MBps). The throttling allowed the temperature to stay below 50 C throughout our benchmark run.
BrandX, though, behaved differently. The temperature in the steady state settled around 53 C. Unfortunately, the throttling (after a similar amount of data transfer as the Mushkin Ventura Ultra) resulted in the write speeds getting capped at a paltry 20 MBps. The reads managed to remain around 80 MBps.
The Mushkin Atom is not meant to take the performance crown, and the advertised write speeds are in the 20 MBps range. Our benchmark run ran at a steady 15 MBps, while the reads didn't get throttled at all in our evaluation process.
The LaCie Rugged Thunderbolt drive is not a flash drive (unlike the other units considered in this piece). It is a bona-fide SSD in a USB 3.0 / Thunderbolt hybrid enclosure. It is no wonder that the transfer rates were hardly affected by the relatively small amount of data traffic. The real winner of our evaluation was the Corsair Voyager GTX. There is no performance degradation even after more than 120 GB of continuous traffic. It must also be remembered that we ran our robocopy benchmark with multiple queue depths in our original review (that was more than 480 GB of continuous traffic) and the table showed remarkable consistency. The instrumented benchmark run confirmed the same.
Coming to the business end of the piece, it must be remembered that the capabilities must be compared keeping the price in mind. If cost is not an issue and the form factor is not an issue, the LaCie Rugged Thunderbolt is the hands down winner for a fast portable DAS unit with consistent performance. If cost is the primary concern, and one doesn't mind a little bit of throttling after around 18 GB of continuous write traffic, the Mushkin Ventura Ultra is a great choice at less than $0.6/GB. The middle ground (right balance of cost and fast, consistent performance, along with a traditional flash drive form factor) is held by the Corsair Voyager GTX. At more than $0.85/GB, it also serves as a reminder that one gets what they pay for.
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jabber - Sunday, November 16, 2014 - linkI have one of these and yes when it hits its stride it really flies but sometimes it seems rather picky with what USB3.0 ports it will decide to play ball with.
For some reason I still feel that USB3.0 is at the stage USB2.0 was around 2002 when you had to be careful which chipset (VIA - Bad NEC - Good) you used. It's not fully sorted yet.
Samus - Sunday, November 16, 2014 - linkWhich controller/chipset was the USB host?
ganeshts - Sunday, November 16, 2014 - linkhttp://anandtech.com/show/8241/lacies-2big-thunder...
Intel Z97 ; USB3_1 in the Pro Wi-Fi ac board depicted in the link above. It is directly off the PCH.
Obviously, the same port is used to test all drives.
Samus - Sunday, November 16, 2014 - linkThanks!
OrphanageExplosion - Sunday, November 16, 2014 - linkIs the Brand X flash drive available to purchase now? If it has fundamental flaws, shouldn't you be telling us about it now as opposed to when a nebulous firmware upgrade becomes available?
I assume that the drive is not yet available?
ganeshts - Sunday, November 16, 2014 - linkThe 'fundamental flaw' in BrandX is the same as that in the Mushkin Ventura Ultra. It is just that the extent of throttling is different.
I can safely say that the drive we tested is $150+. If that is your budget, you should choose from the ones that have been named and reviewed in our list.
At AnandTech, we believe in giving manufacturers a chance to resolve the issues before either recommending or not recommending them. In its current state, I will not recommend BrandX, so you should just ignore it while considering possible purchase options. It doesn't matter who the manufacturer is :)
hrrmph - Sunday, November 16, 2014 - link"At AnandTech, we believe in giving manufacturers a chance to resolve the issues before either recommending or not recommending them."
hero4hire - Tuesday, November 18, 2014 - link*sigh* So the shoddy product doesn't lose. The always positive review ad carasoul doesn't lose. Until we get to to the end user everyone wins! Is your audience your readers or the companies providing ads and samples? Its difficult to tell when you are protecting companies. Why not name them, let the reader know there is a fix (or not) planned and protect the people buying the products. You know... Like a review site. If you think its a bad sample then you can communicate that. This everything is Facebook positive thumbs up makes me skeptical of every review blurring into ads.
OrphanageExplosion - Tuesday, November 18, 2014 - linkIf a product is on the market that under-performs, you should be putting the readers first and telling them not to buy it, then re-evaluating the product when it is eventually fixed.
How can I ignore BrandX when you won't tell us what it is? Absolutely unacceptable.
What you are basically saying is that you are holding back a bad review because you don't want to upset the company concerned. Unbelievable... Simple question - who do you write your reviews for: your readers or your suppliers and advertisers?
7Enigma - Tuesday, November 18, 2014 - linkThat is horrible, absolutely horrible and I don't know when Anandtech "switched" to this policy. If the product is pre-production and hasn't come to market then fine. But if you are telling us you are testing a marketed product and won't release the name because of crap performance that is unacceptable. Answer this and then think about it....if BrandX had been awesome would you have kept the name a secret? I thought not...