Top positive review
Plusses and minuses of SMR drives (with December 2018 update)
Reviewed in the United States on October 10, 2016
Update, December 2018
I've been using this for 21 months to back up my MacBook Pro hourly with Time Machine. No problems at all, still works (and sounds, thumpety thump) like it has from the start.
The Backup Plus Hub series appears to consist of SMR (Shingled Magnetic Recording) drives. We know the 8 TB version is SMR because another reviewer (Pacific coast) opened it up (voiding his warranty) and found a Seagate Archive drive, which is SMR. I asked Seagate if the 6 TB version I got is an SMR drive, and they said "Unfortunately, we do not have this information available." Ha ha! Their reticence is understandable, the more common PMR (Perpendicular Magnetic Recording) technology is generally preferred. The prices of these Backup Plus Hub drives are less than Seagate's bare PMR drives of equal capacity, which also supports the idea that the Backup Plus Hub series is SMR.
SMR technology allows more physical bits of memory in the same space without decreasing the size of the bits.
Advantages of SMR
-- Fast burst sequential writes are possible due to higher density and allied technology.
-- Larger drive capacities in same-size enclosures.
-- Cheaper to produce in large capacities.
Disadvantages of SMR
-- Slower random writes. SMR drives use large write heads relative to the width of the tracks of bits, so writing one track affects the next tracks of bits too. This limits SMR drives to sequential writing, where the next tracks don't matter. To do random writes (such as changes to data on the drive already), data must be arranged sequentially in cache, by the drive in this case, and entire sections of the drive must be rewritten sequentially. Some of this can be hidden by the use of large cache on the drive, believed to be 20 GB or more on Seagate SMR drives. Data can be written quickly to cache and then rewritten more slowly to another part of the drive.
-- Highly variable sequential write speeds, due to the particular ways the drive manages where to put data.
Read speeds aren't affected as much.
The consensus about SMR drives is that they're well suited to backup use, which is reflected in the name of this series of drives. They probably aren't as suitable to use as a main drive to run a computer from, and are generally *not* recommended for RAID configurations (which wouldn't be likely uses for a single external drive anyway).
The 6 TB version of this drive hasn't been tested by professional reviewers, but the 8 TB version has tested very well in standard benchmarks in numerous professional reviews, often well over the 160 MBs maximum rate claimed by Seagate. It's been more variable in practical use. I'm unable to test it myself with a USB 3.0 connection, but one professional reviewer who did got an average of 72 MB/s for a write of a little under 90 GB of files. That's a little over 20 minutes. (A customer review here--Pacific coast again--gets a similar 75 MB/s.)
[Update December 2018: Someone asked for speed test now that it's two years old, and since I have a USB 3.0 connection for it now, I was able to test it at full speed. For 20GB of photos from my MacBook Pro it took right about 3 minutes, or 110MB/s write speed. To copy them back took just over 2 minutes, about the rated 160MB/s read speed. I've only used 450GB of the 6TB capacity, so it's not congested yet.]
Differences between Windows and Mac versions
According to Seagate, the only differences between this Windows version and the Mac version of the Backup Plus Hub series are the initial formatting of the drives and the cosmetics of the cases. The formatting can easily be changed at home, so buy whichever drive you please for either OS.
-- Windows 7 or later
-- Mac OS 10.7 or later
-- for Mobile Backup app: iOS 8 or higher, Android 3.0 or higher
-- Doesn't run too hot. I've seen measured temps of 100 and 113 degrees inside, which is fine for a hard drive.
-- A little noisy when operating, not any worse than most computers.
-- No fan, has passive cooling through vents on the bottom.
-- Includes USB 3 (or 2) cable, type A to micro-B.
-- 2-year warranty.