The Cookie Machine - Click here to drag window

DUMMY TEXT - Real text set in assets/js/theCookieMachine.js

Views: 1,339β€…    Votes:  3β€…    βœ… Solution
Tags: partitioning   ssd   performance  
Link: πŸ” See Original Answer on Ask Ubuntu πŸ”—

URL: https://askubuntu.com/q/939990
Title: Samsung SSD 850 Pro slow speed
ID: /2017/07/26/Samsung-SSD-850-Pro-slow-speed
Created: July 26, 2017    Edited:  July 26, 2017
Upload: November 24, 2022    Layout:  post
TOC: false    Navigation:  false    Copy to clipboard:  false


SATA II channel (3 Gbps) vs. SATA III channel (6 Gbps)

Looking at your timings it is similar to my /dev/sdc

$ sudo hdparm -tT /dev/sdc

/dev/sdc:
 Timing cached reads:   20494 MB in  2.00 seconds = 10255.92 MB/sec
 Timing buffered disk reads: 812 MB in  3.00 seconds = 270.63 MB/sec

What you are hoping for is timings like my /dev/sda

$ sudo hdparm -tT /dev/sda

/dev/sda:
 Timing cached reads:   21598 MB in  2.00 seconds = 10809.23 MB/sec
 Timing buffered disk reads: 1566 MB in  3.00 seconds = 521.44 MB/sec

The explanation can be found using dmesg | grep SATA

$ dmesg | grep SATA
[    1.177247] ahci 0000:00:1f.2: AHCI 0001.0300 32 slots 6 ports 6 Gbps 0xf impl SATA mode
[    1.202732] ata1: SATA max UDMA/133 abar m2048@0xf1618000 port 0xf1618100 irq 27
[    1.202735] ata2: SATA max UDMA/133 abar m2048@0xf1618000 port 0xf1618180 irq 27
[    1.202736] ata3: SATA max UDMA/133 abar m2048@0xf1618000 port 0xf1618200 irq 27
[    1.202739] ata4: SATA max UDMA/133 abar m2048@0xf1618000 port 0xf1618280 irq 27
[    1.521294] ata1: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
[    1.521318] ata3: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[    1.521337] ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
[    1.521356] ata4: SATA link up 1.5 Gbps (SStatus 113 SControl 300)

Both /dev/sda and /dev/sdc are SATA III SSD’s but sda is on a 6 Gbps bus (ata1) and sdc is on a 3 Gbps bus.

Comparison to SATA II 500GB HDD on a SATA III Channel

For comparison sakes here are the results of a 5400 rpm SATA II 500 GB HDD running on a SATA III (6 Gbps) channel:

$ sudo hdparm -tT /dev/sdb

/dev/sdb:
 Timing cached reads:   20632 MB in  2.00 seconds = 10325.32 MB/sec
 Timing buffered disk reads: 340 MB in  3.02 seconds = 112.76 MB/sec

Summary

This is a laptop and only has two SATA channels:

Linux/Ubuntu matches the device’s SATA ability and channel’s SATA ability to the lowest common denominator:

⇧ Freeze after computer suspends for the first time in a session dell-wmi-dkms errors when updating  β‡©