Thunderbolt, the high-speed interconnect standard, launched in February 2011 with Apple’s springtime updates to the MacBook Pro. Yet useful products to use it remain relatively thin on the ground. Elgato’s Thunderbolt SSD is one of very few portable storage drives to use Thunderbolt. It’s a fast drive but it also highlights some current issues with the implementation of the standard that means it cannot perform close to its potential. Read more Storage reviews.
Elgato is best known for its digital TV adaptors, enabling digital terrestrial and satellite television to be watched on a Mac or Windows PC. And the company has an even longer background in digital media, commissioned to develop Roxio’s CD burning technology, for example. But the Elgato Thunderbolt SSD is the company’s first storage product.
The Elgato Thunderbolt SSD comprises a 2.5in solid-state drive in a compact all-metal enclosure, with a single Thunderbolt port to connect to an Apple Macintosh, or a Windows PC fielding a Thunderbolt-enabled motherboard. It requires no extra connection as it takes its power from the Thunderbolt bus, like most portable USB and FireWire hard drives.
Thunderbolt allows up to 12 devices to be connected to one port, daisy-chained together, and up to one display at the end of the chain. Bus-powered units like this SSD are however only permitted to offer one Thunderbolt port. So unlike FireWire, which will allow two portable drives to be linked in-line to one port, bus-powered Thunderbolt devices can only work at the end of a chain.
Elgato Thunderbolt SSD: Build Quality
The Elgato Thunderbolt SSD is a solid-feeling hunk of metal, comprising two halves of cast aluminium secured together by four hex-head screws.
It’s finished with gunmetal paint over the natural metal, and this finish can chip off with use.
One such screw has been glued over to discourage removal. In fact Elgato explicitly warns against opening the case. If you should dare to open the case, you may find a message adhered to the inside of the top half that reads:
‘Welcome! We’ve been expecting you.
This Elgato Thunderbolt SSD was carefully engineered and tested for reliability and performance. Do not replace the factory-installed SSD.
Peak power consumption of the SSD may not exceed 3.5W
Please understand that opening the case has voided your warranty.’
The solid-state drive already fitted inside is an older SATA Revision 2.0 device from SanDisk, the Ultra 120 in our example.
Given Thunderbolt’s design specification of up to 10Gbps full-duplex (that is, 10Gbps in each direction simultaneously), which is equivalent to 1250MBps, there ought to be bandwidth to spare to use a third-generation SSD that is capable of at least 500MBps sequential read/write speeds.
The SanDisk Ultra 120 SSD itself is limited to around 280MBps performance.
We were told that this older, slower drive was selected due to restrictions imposed on the power budget.
While Thunderbolt’s original spec stated that 10W is available to bus-powered devices, the internal SSD is left short-changed by the high power requirements of the essential supporting electronics.
(An Intel spokesman, Jason Ziller, Intel Director of Thunderbolt Marketing, told us that the Thunderbolt bus has been revised to allow up to 12W of power, although Thunderbolt devices are still currently limited to drawing 10W maximum.)
For a start, the Thunderbolt cable itself consumes several watts; the latter cable is an active transmission-line device, with two power-hungry chips hidden inside the plugs on each end.
So while Thunderbolt may deliver up to 10W of power, only 3.5W is available for the SSD, as Elgato warns in the label inside the case.
In use, the unit could get conspicuously warm to the touch but the case serves well as a heatsink to drain excess heat away. We also tried a SATA 6Gbps SSD though, and discovered why Elgato did not fit the same.
Elgato Thunderbolt SSD: Performance
Used as intended, the Elgato Thunderbolt SSD is quite quick for a portable external storage drive. From the QuickBench speed benchmark, we saw write speeds up to 264MBps, and sequential read speeds up to 271MBps.
From the QuickBench small-file transfer test (using samples from 4kB to 1024kB), we saw average sequential read/write speeds of 139/140MBps.
In the random read/write test with same small files, performance was still very good at 127 and 139MBps respectively.
Do note the near-symmetrical speeds of read and write performance. This suggests that QuickBench is using compressible data in its data transfer calculations.
Unfortunately the SanDisk Ultra 120 uses a SandForce controller, which accelerates write performance by pre-compressing incoming data. While this allows good performance from data that is compressible – such as text files and spreadsheets – it behaves much less well with already-compressed media files such as JPEG, MPEG and MP3 files.
So we tried the Elgato Thunderbolt SSD with a benchmark test that can give closer results to real files, CrystalDiskMark running in Windows 7, focusing on its random data set.
When measuring sequential performance with a string of zeroes, it returned read/write figures of 253/240 MBps.
When measuring random data – which is closer to the character of compressed media files – speeds dropped to just 205/118 MBps.
Pushing the power envelope
With Elgato’s consent, we tried a third-gen SATA SSD to see how the unit behaved. As predicted, when we slotted in the drive – a Patriot Wildfire 256GB SSD – connection to the host PC became erratic as the drive would randomly disconnect. This was presumed to be whenever it became temporarily starved of sufficient power during peak transient current demands.
When this SSD was working though, we noted it was performing some way below its capabilities. Fastest sequential read speeds were up to 382MBps, while fastest writes were at 347MBps
An Intel 520 SSD was also tried, with somewhat similar results: 382MBps reads and 343MBps writes.
The Patriot Wildfire 240GB was previously tested under Windows on a direct SATA 6Gbps link, where we saw it able to reach speeds of around 500MBps (read) and 470MBps (write); the Intel could reach 488 and 480MBps in the same CrystalDiskMark test.
Further examiniation of the the Elgato Thunderbolt SSD’s electronics revealed the probable reason why the two SATA Revision 3.0 SSDs we tried were being throttled back – one of the key components in the Elgato’s supporting electronics is the PCI-Express to SATA bridge.
In this case an ASMedia ASM1061 chip is used. While this device is listed as supporting ‘SATA 6BGps’, it uses only a single PCI-E lane.
This gives it a theoretical 500MBps throughput at the PHY level, but in practice may only be able to funnel data through at around 75% its nominal ceiling. This at least would explain the circa-380MBps ceiling on data transfer speeds from the Elgato Thunderbolt SSD.