MP 1,1-5,1 Slow copy of files on OpenCore Big Sur?

[TECK]

I have Big Sur installed on a NVMe disk with decent read/write speeds, on my cMP 5,1.

Specs from signature:
cMP 5,1 2x3.46Ghz 96GB | Sapphire Pulse RX 580 | Syba SI-PEX40129 970 EVO Plus | Sonnet Allegro USB3C-2PM-E | Broadcom BCM943602CDPAX

I noticed that performing a copy for a set of large files is quite slow. If my writes are approx. 2GB/s, copying 86GB should take approx. 45 seconds. Look at the crazy numbers:

$ du -h files
86G    files

$ time cp -a files files-new
real    2m16.922s
user    0m0.145s
sys    1m2.150s

$ time /bin/cp -R files files-new
real    2m17.546s
user    0m0.149s
sys    1m3.382s

No other disk or CPU related tasks are running during copy. On the opposite side, performing a delete is quite fast:

$ time rm -rf files-new
real    0m3.446s
user    0m0.001s
sys    0m0.253s

Can you please help me understand what do I miss and why the copy time is double than expected? Thank you.

 

[h9826790]

You copy a files onto the same drive means need to do BOTH read and write on the same drive at the same time. Therefore, you won't have 2000MB/s.

The Blackmagic benchmark only benchmark pure read or pure write, but not at the same time.

 

[tsialex]

You copy a files onto the same drive means need to do BOTH read and write on the same drive at the same time. Therefore, you won't have 2000MB/s.

The Blackmagic benchmark only benchmark pure read or pure write, but not at the same time.

Another thing to consider is the size and number of files. One 10GB contiguous file will be transferred at nearly benchmark speeds, while 1000 100K files will take a lot of time.

 

[TECK]

They are all 2-3GB files. Now I understand why almost double the write time, is technically read+write time, thank you for useful explanation.