Thunderbolt 2 Drive Is Slow to Write

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Level 2

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Thunderbolt 2 Drive Is Slow to Write

I'm running Monterey on a Mac Pro (Late 2013), 2.7 GHz 12-Core Intel Xeon E5, 48 GB 1866 MHz DDR3. This machine is still a rocket and I have no problems with its performance.

I have a myriad of external USB drives, both SSD and SATA. But I decided to put to use the four Thunderbolt 2 ports on the back and bought an OWC ThunderBay 4 mini Four-Bay External Drive Enclosure with Dual Thunderbolt 2 Ports. I added two WD SATA drives and started backing up files to them, with no problems.

But I've noticed that writing files to this drive bay is surprisingly slow, compared to my other USB drives. I work in Photoshop a lot and hit SAVE often, and yes, these are pretty good size files. But they take a lot longer than I'm used to.

What's up with that? I thought any version of Thunderbolt was faster than USB 3.0?

Thanks.

Mac Pro, macOS 12.7

Posted on Oct 2, 2023 7:39 PM

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Answer 1

Best reply

Grant Bennet-Alder

Level 10

127,945 points

Oct 3, 2023 5:14 AM in response to Tom Hanser

when you provide a data highway faster that the top speed of the drive, it does not make that slow drive any faster. It merely eliminate bottlenecks, and keeps the data highway speed from clipping and slowing down your drives.

Typical top speed for a rotating magnetic drive is between 50 and 100 M Bytes/sec. The limiting factor is the rotation speed, which determines how fast bits can sweep under the Read/Write head.

ThunderBolt-2 runs up to 20,000 M bits/sec, ballpark 2,000 M Bytes/sec, so at 20 times faster than the drive cab produce data, you can be sure that Thunderbolt-2 Bus speed is not slowing your data in the slightest. But speed up your data? No, it does not work that way.

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Answer 2

Tom Hanser Author

Level 2

170 points

Oct 3, 2023 7:12 AM in response to Grant Bennet-Alder

Understand, and thanks so much, Grant.

It's not the bus that's slowing me down, it's the SATA drive itself.

- Seagate 4TB BarraCuda 5400 RPM 128MB Cache SATA 6.0Gb/s 2.5" 15mm Laptop Internal Hard Drive ST4000LM024

- WD40EZRX Western Digital 4TB Internal Hard Drive IntelliPower 64MB Cache SATA 6.0Gb

I needed BIG drives to store a lot of files (images, video, project files) so I opted for these SATA drives.

Again, thanks for your explanation.

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Answer 3

Oct 3, 2023 10:00 AM in response to Tom Hanser

your top item, Seagate ST4000LM024 claims it can transfer a Burst of data in or out of its buffer RAM at up to 140 M Bytes/sec, but can not source data off the platters that fast. It is a 5400 RPM drive with 128 M Bytes cache. At only 15 mm thick, it is a notebook computer drive, built for low power draw, not speed.

WD40EZRX appears to be a 5400 RPM drive as well, and as you said, has a 64 M Bytes buffer. Green drives like this one are also optimized for low power and low heat generated, not for speed.

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Answer 4

Tom Hanser Author

Level 2

170 points

Oct 3, 2023 10:50 AM in response to Grant Bennet-Alder

Thanks for your explanation, Grant.

Initially, I was going for large storage backup drives, which is what they're for. I shouldn't be working off them repeatedly, and that's what I have SSD drives for.

That drive bay from OWC only takes four small 2.5" drives, but perhaps I purchased the wrong drives? I was looking for at least 4TB drives, and I normally purchase WD or Seagate.

It was an attempt to utilize my Thunderbolt 2 ports, which are staring me in the face but until I recently added a second monitor, were not in use.

Thanks again.

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Answer 5

Oct 3, 2023 1:34 PM in response to Tom Hanser

Well you did get fairly large. What you did not get is especially FAST.

That setup would make a Great Time machine destination, because Time Machine works at low priority in the background, and does get any extra benefit from drives that are fast.

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Thunderbolt 2 Drive Is Slow to Write

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