I have recently installed Ubuntu 17.04 on a brand new Samsung SSD 850 Pro. It seems to work fine. However the read and write speeds are roughly half of advertised
$ sudo hdparm -tT /dev/sda
/dev/sda:
Timing cached reads: 9012 MB in 2.00 seconds = 4507.79 MB/sec
Timing buffered disk reads: 808 MB in 3.01 seconds = 268.75 MB/sec
AHCI is enabled in BIOS and the system boots on UEFI.
The SSD has 6 partitions
$ sudo fdisk -l
Disk /dev/sda: 238.5 GiB, 256060514304 bytes, 500118192 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 8AAFFE6D-A829-46B5-B46F-ED4F7432F5B5
Device Start End Sectors Size Type
/dev/sda1 2048 485375 483328 236M EFI System
/dev/sda2 485376 39544831 39059456 18.6G Linux filesystem
/dev/sda3 39544832 117671935 78127104 37.3G Linux filesystem
/dev/sda4 117671936 133294079 15622144 7.5G Linux swap
/dev/sda5 133294080 259123199 125829120 60G Linux filesystem
/dev/sda6 259123200 468838399 209715200 100G Linux filesystem
Is there a problem in my setup? What might be the reason for lower than expected speeds? Any input is appreciated.
Thanks in advance!
Update
Forgot to mention that the SSD is mounted on a 2010 Dell Latitude E6410 which I have just learned that has a SATA II connector. It seems then, the speeds I am getting are reasonable.
Thanks everyone for their comments and answers!
Best Answer
SATA II channel (3 Gbps) vs. SATA III channel (6 Gbps)
Looking at your timings it is similar to my
/dev/sdc
What you are hoping for is timings like my
/dev/sda
The explanation can be found using
dmesg | grep SATA
Both
/dev/sda
and/dev/sdc
are SATA III SSD's butsda
is on a 6 Gbps bus (ata1) andsdc
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:
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: