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I just purchased a new Plextor M6V 512GB SSD and am experiencing very low 4K Q32 read speed. 36 MB/s = ~9,000 IOPS which is 10 times as low as specification value. Why could it be?
And here is the same SSD's benchmark result but on my laptop.
Jofsey
Posted 2016-07-16T10:50:11.513
Reputation: 917
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The fact that the 4K random speeds did not increase as much as expected when the queue depth is increased to 32 probably means that NCQ is not in effect.
Usually that's because SATA mode is not AHCI but IDE compatibility. In Linux that can be caused by the boot parameter libata.force=noncq.
P.S. In my past experience, when my SSD suffered performance impact because of that, the 4K QD32 read speed was also held back more than the 4K QD32 write speed. Not sure if it's a coincidence though.
Tom Yan
Posted 2016-07-16T10:50:11.513
Reputation: 4 744
So what would be the steps to fix this? – fixer1234 – 2016-07-17T21:18:54.840
It looks as though your SSD is performing as others are according to your link signifying that you are not getting low IOPs. So is your question actually "why is manufacturer IOPs spec a higher than real world performance?" – Damon – 2016-07-16T11:06:19.330
I'm curious as to why the 4K random read is slower than writes. Have you re-run the test to see if it was a fluke? Can you let your system boot, then wait for about 10 minutes before running the benchmark, it might be services starting up or programs hogging the read. – Mokubai – 2016-07-16T11:08:25.793
@Damon I've just made a more comparable benchmark of the same drive on different PCs and updated my question. – Jofsey – 2016-07-16T11:35:22.333
How old is the desktop? What is the motherboard? – Mokubai – 2016-07-16T11:54:24.877
@Mokubai Motherboard: ASUS P8H77-V LE, release date: Feb 2012, SATA 6 – Jofsey – 2016-07-16T13:16:42.057
3Is the SATA mode AHCI? It looks like NCQ is not in effect. – Tom Yan – 2016-07-16T14:08:00.430
@TomYan I've enabled ADCI and got 243MB/s. Thank you very much! I'll accept you answer if you transform the comment into it. – Jofsey – 2016-07-16T14:40:36.800