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Thoughts on HDD and SSD speed

December 16, 2018 — BarryK

I posted a tutorial recently about installing EasyOS to a new 2.5inch SATA3 on my Mele PCG35 Apo mini-PC:

...where I reported a write speed of 63MB/sec to the SSD. However, that is going through some bottlenecks, a file was being copied from my SanDisk Extreme USB-stick. The SanDisk Extreme, though, is a very fast drive, so that 63MB/sec is a bit disappointing.

The manufacturer claims "read and write speeds up to 500MB/s and 450MB/s", see here:

Well, we can do some simple tests, eliminating some bottlenecks. Mostly, I am interested in sequential read and write, of large files. So, creating a 411MB file 'easy.sfs' in /tmp, then write this to the SSD. /tmp is a tmpfs and the contents of /tmp will reside in RAM (unless paged-out to a swap partition). Here we go:

# dd if=/tmp/easy.sfs of=/mnt/sda2/easy.sfs bs=1M conv=fsync status=progress oflag=sync

...we get 153MB/sec. Much better!

Doing the reverse, reading from the SSD, we get 431MB/sec. Faster, as expected. Note, I had to be very careful with how it is done in reverse, rebooted first, to make sure everything was flushed from the virtual memory.

Testing with a USB3 2.5 inch HDD on the Mele:

Write: 56.7MB/sec
Reboot then read: 91.9MB/sec

Over on my HP mid-tower PC, with an internal 5400 RPM SATA HDD, running the same sequential write and read test:

Write to HDD: 19.6MB/sec
Reboot, then read from HDD: 139MB/sec

Confirming the SSD is vastly superior. The HDD is going to go downhill when there is defragmentation, or when reading and writing lots of small files, further showing the superiority of the SSD.   

Tags: tech