Local write speed on share (/mnt/user/data) is 3x slower than on disk (/mnt/disk/sdb1)

[Jack462937]

I'm new to unraid and learning the settings as I go, but I have run into a problem.  

 

Unraid 6.8.2

I removed parity and cache to debug problem.  

Only 2 disks.

Disk A works great.       180 MB/s                                     (SATA on motherboard) 

Disk B gets 1/3rd throughput when mounted in share.      (usb3.0 connection to 2.5" HDD) 

Share is setup to only use disk B. 

 

On unraid host: 

/mnt/disk/sdb1:    dd ... bs=1G            105 MB/s  

/mnt/user/data:   dd ... bs=1G            33 MB/s  

 

 

Any ideas of what to tweak?  

 

I found that adding the 'oflag=direct' argument to dd, fixed the problem for local host.   
but with a remote CIFS mount I still see ~30MB/s.       

I'm looking for corresponding async or directio param for cifs.  

Edited March 28, 2021 by Jack462937
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[trurl]

1 hour ago, Jack462937 said:

Disk B ...      (usb3.0 connection to 2.5" HDD) 

USB connections aren't recommended for disk in the parity array or pools. USB connections are often not "permanent" connections and if it disconnects the disk will be kicked out and require rebuilding.

[Jack462937]

Thanks trurl.   

I suspected the different driver might be causing the issue.  

I guess I can live with it until I upgrade for more SATA ports.