How to investigate slow WRITE performance over SMB?

MasterLog

Cadet
Joined
Jun 2, 2023
Messages
3
Hello,
I have just installed TrueNAS-SCALE-22.12.3.3 over a simple server (4 Core CPU, 16GB) running ProxMox 8.
At the moment it's the only VM running, and it has direct access to SATA controller (with the SSD) and the NICs. Everything run fine, but once from a Windows PC I am trying to copy a file 2GB over SMB after some time the writing performance drop dramatically, as the examples below:
WRITE.png
WRITE2.png


Here is the console once the performance drops:
Screenshot 2023-09-16 at 18.11.00.png


Once reading the same file, performance are fine (full 1Gbps):
READ.png


I may believe that the there could be some caching for the initial 1GB+ but the performance after that are pretty low (e.g. 4min to copy a 2GB file, 8MB/s on average). To clarify, the pool consists in a single SSD (I will add more drives later after some tests), but connecting it to a PC has shows much higher RW performance (as expected from a consumer SSD). There could be some IO WAIT which seems confirmed by the wa shown on "top", so I have run iostat as below:
Screenshot 2023-09-16 at 18.10.52.png


I am not really sure if those are showing anything specific, so can you please give me some suggestions to improve those performance?
Previous thread didn't help.

Thanks!
MasterLog
 
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