These days, flash-based storage is nothing short of amazing. There are numerous options for extremely compact, blazing fast storage at increasingly affordable prices. High-speed interfaces come highly recommended as flash memory sizes top 32 GB—which is to say, 64 GB or more—because a slow flash drive can be painfully slow indeed.
Fortunately, there are numerous interfaces available that make sense in a variety of situations and across a broad range of machines. In this story, I'll march through those interfaces, and explore the kinds of high-speed, flash-based storage options available for each one.
A Tale of Three Interfaces: USB 3.0, eSATA, and mSATA
Though there are many more options for flash-based storage available in today's marketplace, for this story I concentrate on three popular options because they offer a good combination of high speed and broad availability.
Let's explore these three interfaces, along with their speeds and feeds, and some of their pros and cons, in the sections that follow.
USB 3.0 Flash Drives
These devices are more-or-less standard USB flash drives (UFDs) with circuitry that supports the latest—and fastest—version of USB (version 3.0, also known as SuperSpeed). Figure 1 shows the official USB 3.0 logo.
Figure 1 USB logo
The USB 3.0 interface supports theoretical speeds of up to 5 Gbps (625 MBps), with real-world read speeds coming in at just 63 Mbps (about 10% of the theoretical maximum). In practice, write speeds max out below 51 Mbps (just over 8% of the theoretical maximum).
For a nice collection of community data on USB drives, see Nir Sofer's excellent USB Flash Drive Speed Tests page for a general source of data and comparisons. Use those numbers to set your expectations for USB 3.0 UFD data rates, and you won't be disappointed.
eSATA Flash Drives
These devices look much like UFDs (see logo in Figure 2), except they plug into an eSATA connector instead of a USB port.
Figure 2 eSATA logo
eSATA extends internal Serial AT Attachment (SATA) connectors outside a computer's case or enclosure. Whereas eSATA used to appear only on desktop PCs, it is increasingly common on higher-end laptops as well.
Although USB 3.0 does make eSATA more of a frill than it used to be, it's still a great way to attach external drives of any kind—including SSDs, conventional hard disks, and even small form-factor flash drives—to a notebook or desktop PC. SATA's top speed these days is rated at a theoretical maximum of 6 Gbps (revision 3.0), though older versions top out at 1.5 Gbps (revision 1.0) and 3.0 Gbps (revision 2.0, the source for the logo shown in Figure 2).
Most newer (post-2009) PCs and notebooks support the 6 Gbps version, whereas older machines typically top out at 3 Gbps. A study published on the Tom's Hardware website in 2009 shows that eSATA flash devices can deliver write speeds in excess of 65 Mbps, with top write speeds in excess of 45 Mbps, and drive interface bandwidths (which set the upper limit on attainable peak read and write speeds of 53 to 66 Mbps).
mSATA Flash Drives
Variously decoded as the Mini-Serial ATA or Micro-SATA interface, this small form-factor applies to entire solid state drives, rather than easy-in/easy-out removable drives like those described under the two preceding headings (see the logo in Figure 3).
Figure 3 mSATA logo
But because mSATA drives are increasingly available, surprisingly affordable, and extremely compact, they're worth considering in two specific sets of circumstances:
- On notebooks or PCs that include mSATA slots, it's often a good idea to incorporate these devices, either to take advantage of Intel's Rapid Start technology (link to PDF user guide) to create a high-speed disk cache, or to set up as an independent boot or data drive. Given that many new notebooks (I've had good luck with this technology in my two 2012 vintage Lenovo notebook PCs: an X220 Tablet and a T520 laptop) include an interface for WWAN that also accommodates mSATA devices, it's definitely worth looking into the suitability of mSATA on such machines. See Figure 4.
- On desktop PCs with unused PCI-e slots, inexpensive adapters convert mSATA to SATA and grab power from the PCI-e infrastructure, so you only need to run a standard SATA cable from the interface into an unoccupied SATA port on your PC. This setup will not support Rapid Start, but it will permit use of any mSATA drive. With mSATA capacities now as high as 240 GB, this can be an excellent way to add high-speed storage to just about any modern desktop PC nowadays.
Figure 4 This mSATA to SATA adapter accommodates an mSATA SSD in a PCI-e x1 slot, with a SATA data output to your PC's SATA connectors at 1.5, 3.0, or 6.0 Gbps (cost $28).
mSATA works more or less the same way as regular SATA, and because it uses high-speed SSD drives built to its specific form factor (typical dimensions are 51mm x 30mm or 2.007" x 1.18") these diminutive devices offer speeds entirely on par with other SSD drives. That puts read speeds between 250 and 500 MBps, depending on the size, make, and model of drive involved, with read speeds in the same general ballpark. Much faster than either USB 3.0 or eSATA flash drives, in other words.
Top Contenders for USB 3.0 Flash Drives
In comparison tests and based on buyer's feedback and reviews, the following makes and models jump to the head of this sizable class of products, where offerings between 64 and 128 GB in size typically sell for between $75 and $150:
- Kingston DataTraveler Elite 3.0 (capacities: 16, 32, 64 GB; fast and affordable)
- Corsair Flash Voyager USB 3.0 (capacities: 16, 32, 64 GB; fast and more expensive, very sturdy)
- Patriot SuperSonic Magnum USB 3.0 (capacities 64 and 128 GB; fast and more expensive, also sturdy)
Top Contenders for eSATA Flash Drives
Since the introduction of USB 3.0 in 2010, interest in and product offerings for eSATA flash drives have waned. Most drives of this type will work either in a USB or eSATA port, but support only USB 2.0. This makes the remaining products still available in a smaller class than USB 3.0, where offerings typically run from 16 to 64 GB in size (higher capacities are available but often prohibitively expensive):
- KingSpec SSD (16 GB eSATA/USB 2.0; reasonably fast and moderately priced at $43; 32 GB $95)
- SuperTalent eSATA SSDs (8, 16, 32, 64 GB eSATA/USB 2.0; fast but expensive)
Top Contenders for mSATA SSDs
This niche is exploding with excellent products in capacities from 32 to GB, at prices from $50 to $289. Byte for byte, mSATA drives still cost more than packaged 2.5" SSDs, which is hard to swallow, given that the internal circuitry is more alike than different between these two drive classes. Nevertheless, prices are incredibly affordable on mSATA drives now, and they make terrific add-ins for suitable notebook and desktop PCs.
Here are some top contenders in this burgeoning product niche:
- Mushkin Enhanced Atlas Series (60, 120, 240 GB, $75-230, fast and affordable)
- Crucial M4 Series (32, 64, 128, 256 GB, $51-207, fast and affordable)
- Intel 310 Series (40, 80 GB, $61-190, fast but more expensive)
- OCZ Nocti Series (30, 60, 120, $50-110, fast and affordable)
With eSATA flash drives now mostly a historical curiosity, buyers in need of fast easy-in/easy-out external storage will probably want to consider the capacities they need and the costs they can tolerate as they choose between USB 3.0 and SSD devices. For about $29, buyers can package an mSATA drive in a 1.8" USB 3.0 external case, which is incredibly compact, even if not as small as a typical USB flash drive.
Given higher prices for many USB 3.0 UFDs of 64 GB or more in capacity, it may actually be a better deal to buy an mSATA drive, buy an enclosure, and use an external SSD instead of a UFD. It may not only be a little cheaper (or perhaps better than that); it will probably also be faster, too.
The only reason I can see for buying an eSATA flash device any more is for those PCs or notebooks that lack USB 3.0, but offer eSATA ports. Think carefully before you walk this path, though: you may be able to throw in a PCI-e or PCI Express USB 3.0 card or adapter and purchase a USB 3.0 flash device more cheaply than its eSATA counterpart!
After researching this story, I'm inclined to believe that using an mSATA SSD with a USB 3.0 enclosure may actually provide the best of both worlds, for systems where direct SATA or mSATA attachments are impossible or impractical.