Disk speeds

posted on 09:43 PM on Tuesday 28 January 2020

Wondered how fast the various disk options are on the Mac. So I did a little test using dd for writing since it was available on Linux and Mac.

First up is the internal SSD of a MacBook Pro (15-inch 2019).

time sh -c "dd if=/dev/zero of=test bs=1g count=10 && sync"
10+0 records in
10+0 records out
10737418240 bytes transferred in 6.449485 secs (1664848920 bytes/sec)

real    0m6.801s
user    0m0.003s
sys    0m4.580s

So 1506 MB/s write speed which is very very impressive.

Next up is the WD 4TB USB hard drive connect to the same MacBook Pro.

time sh -c "dd if=/dev/zero of=test bs=1g count=10 && sync"
10+0 records in
10+0 records out
10737418240 bytes transferred in 118.254275 secs (90799409 bytes/sec)

real    1m58.825s
user    0m0.003s
sys    0m5.544s

This translated to about 86 MB/s which means that the MacBook Pro is 18 times faster which is ridiculous.

Moving on to the Linux server with its 8x6TB ZFS.

time sh -c "dd if=/dev/zero of=test bs=1G count=10 oflag=dsync && sync"
10+0 records in
10+0 records out
10737418240 bytes (11 GB, 10 GiB) copied, 34.4002 s, 312 MB/s

real    0m39.161s
user    0m0.008s
sys     0m10.626s

Not bad at 261 MB/s, about 1/6 of the speed of the MacBook Pro’s SSD. Not too bad.

Moving to the internal SATA Samsung 860 EVO SSD.

time sh -c "dd if=/dev/zero of=test bs=1G count=10 oflag=dsync && sync"
10+0 records in
10+0 records out
10737418240 bytes (11 GB, 10 GiB) copied, 6.01736 s, 1.8 GB/s

real    0m11.691s
user    0m0.003s
sys     0m6.799s

So that is about 876 MB/s which is plenty fast, about half of the speed of the MacBook Pro.

And lastly an old Samsung 850 EVO SATA SSD connected via USB.

time sh -c "dd if=/dev/zero of=test bs=1G count=10 oflag=dsync && sync"
10+0 records in
10+0 records out
10737418240 bytes (11 GB, 10 GiB) copied, 50.5551 s, 212 MB/s

real    0m54.865s
user    0m0.004s
sys     0m11.396s

That is about 187 MB/s which is not too bad, definitely in USB 3.0 range.

Tried it on the work iMac (Retina 5K, 27-inch, Late 2014) too.

time sh -c "dd if=/dev/zero of=test bs=1g count=10 && sync"
10+0 records in
10+0 records out
10737418240 bytes transferred in 27.654730 secs (388266969 bytes/sec)

real    0m28.034s

user    0m0.003s
sys    0m7.002s

That works out to 365 MB/s which is quite different compared to a modern Mac like the MacBook Pro.

Using a SanDisk Extreme Pro 128GB thumb drive on the iMac with a USB 3 5 Gb/s connection (500 MB/s).

time sh -c "dd if=/dev/zero of=test bs=1g count=10 && sync"
10+0 records in
10+0 records out
10737418240 bytes transferred in 30.610137 secs (350779817 bytes/sec)

real    0m31.575s
user    0m0.003s
sys    0m6.592s

The thumb drive is pretty fast at 324 MB/s which is about as fast as the internal SSD on the iMac.

Next up is a SanDisk Extreme Portable SSD connected to the MacBook Pro.

time sh -c "dd if=/dev/zero of=test bs=1g count=10 && sync"
10+0 records in
10+0 records out
10737418240 bytes transferred in 21.986881 secs (488355680 bytes/sec)

real    0m24.541s
user    0m0.003s
sys    0m5.322s

That is a transfer speed of 417 MB/s which is really quite fast for a portable drive. It has definitely benefited from the USB 3.1 Gen 2 which provides a 10 Gb/s connection.

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