I was always wondering why the read speed of my ssd drive was only about 35 Mb/s when using Gtkhash to check shasums. And the other day I had a value about 80 Mb/s.
Thought my ssd was damaged. But then I found that this was related to the cpu speed.
So I changed the speed to performance and I got read speed of 120 Mb/s.
When I use
sudo hdparm -Tt /dev/sda
to check read speed of ssd I get
/dev/sda:
Timing cached reads: 7742 MB in 2.00 seconds = 3872.89 MB/sec
Timing buffered disk reads: 820 MB in 3.01 seconds = 272.80 MB/sec
but my CPU is running only on 800 Mhz.
So why I’m getting 272 MB/s running on 800 Mhz and only 120 MB/s when using gtkhash when the CPU Speed is 3.3 Ghz?
In general: Is the reed speed of ssd somehow related to the cpu speed when using different programs?
And why do I get only 120 MB/s in Gtkhash when the ssd is capable of 272 MB/s?
disk read/write speeds, absolutely depend on how busy (or not) your CPU is, irrespective of the OS used. except for a few systems (DMA) which allow disk I/O to be performed partially bypassing CPU, a busy CPU will hamper disk I/O. there are plenty material explaining why, if you are willing to search for it.
Gtkhash is measuring how fast your system does hash calculations, not disk speed. Doing hash calculations is cpu work so obviously it depends on cpu speed.
That hdparm command is the simplest way to measure actual disk speed. If you want more comprehensive benchmarking then fio is available in packages but that will require reading the manual because it’s complicated to use. Some examples of usage at the end of this article - How fast are your disks? Find out the open source way, with fio | Ars Technica