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Price
…the cost per gigabyte counts heavily in our evaluations. That said, the star rating is weighted more toward the quality of the product, not how much it costs. But all things being equal, the cost per gigabyte can tip the scales.
Basic performance obviously depends on the technology involved: HDDs, SSDs, USB, Thunderbolt, etc… We run benchmarks and perform real-world operations to determine its speed relative to others of the same ilk. Performance relative to a device’s peers as well as in the grand scheme counts greatly in the final rating. There’s far more granular info on our testing methodology and consideration below.
Durability
Of course, speed is nothing if a device gives up the ghost in six months. HDD failure has become progressively rarer since the bad old days when up to 15 percent of hard drives failed per year. Early SSDs also had their issues, but the only problem we’ve heard of recently was with the SanDisk Extreme Pro line . Every SSD we’ve tested is still going strong, as are all the hard drives from the last five years or so.
That said, SSDs are still a relatively young technology, and NAND blocks/cells can only be written to so many times. We make special note of the TBW ratings for SSDs. That’s an acronym for terabytes written , or the number of terabytes that may be written before a drive runs out of replacements (overprovisioning) for worn-out cell blocks.
MTBF (mean time before failure ) ratings for HDDs are a guess at best, and rarely accurate or provable, so we generally don’t pay attention them.
Seagate Ultra Touch HDD
<div class="lightbox-image-container foundry-lightbox"><div class="extendedBlock-wrapper block-coreImage undefined"><figure class="wp-block-image size-large enlarged-image"><img decoding="async" data-wp-bind--src="selectors.core.image.enlargedImgSrc" data-wp-style--object-fit="selectors.core.image.lightboxObjectFit" src="" alt="Seagate Ultra Touch HDD" class="wp-image-2045473" width="1200" height="674" loading="lazy" /></figure><p class="imageCredit">Seagate Ultra Touch HDD</p></div>
</div></figure><p class="imageCredit">Seagate Ultra Touch HDD</p></div>
Given the limited time we have between testing and publication, 100 percent accuracy on long-term reliability is impossible. We keep our test units in service, but it can take years for a problem to crop up.
One thing we can check is how well an external device sheds heat — the general enemy of electronics. If the temperature of an SSD gets too high, the controller will slow down/throttle operations to reduce said temperature to avoid damage to the components.
We also check the quality of construction and the materials used. With SSDs, shock mounting and shock resistant silicone covers are plusses, but with HDDs they’re an absolute must.
Many devices are IP rated — i.e., designed and tested to ward off dust and liquids. We’ll always discuss this with any ruggedized device, and it does score brownie points.
Portability
When it comes to portability, smaller is obviously better. Thumb drives are generally the smallest and most portable. Their integrated Type-A or occasionally Type-C connector eliminates the need for an additional USB/Thunderbolt cable or power adapter, which takes up space and which you must remember to bring with you. If a device is designed to be portable, the overall ease of transport is obviously considered.
Corsair E1000U
Corsair E1000U
Jon L. Jacobi
<div class="lightbox-image-container foundry-lightbox"><div class="extendedBlock-wrapper block-coreImage undefined"><figure class="wp-block-image size-large enlarged-image"><img decoding="async" data-wp-bind--src="selectors.core.image.enlargedImgSrc" data-wp-style--object-fit="selectors.core.image.lightboxObjectFit" src="" alt="Corsair E1000U" class="wp-image-2348633" width="1200" height="454" loading="lazy" /><figcaption class="wp-element-caption"><p>Corsair E1000U</p>
Jon L. Jacobi
</div></figure><p class="imageCredit">Jon L. Jacobi</p></div>
Devices designed for your desktop might be portable to a degree, but a bit of size and heft is in order. Anyone who’s ever inadvertently sent a small, light drive flying across the table (or room) understands. It’s especially true for 2.5-inch external hard drives, which can’t absorb nearly as many G’s as an SSD. With desktop drives, we also rate such stability — i.e., we check for non-skid feet, etc.
Power requirements
AC adapters are required with 5.25-inch hard drives (still the only way to get more than 8TB in a single unit!), and with very large-capacity USB 3.x SSDs. Single, external 2.5-inch hard drives rarely require an AC adapter; however, some RAID units with more than one drive will. At least non-Thunderbolt types.