Long pauses when writing large files over SMB

[GreaseMonkey88]

Hi guys,

I have the problem, that when I write large files (several GB, > ~5GB) the transfer pauses after some seconds of transferring data. These pauses are up to 10-20s.

I also checked iostat (zpool iostat -v 1). Even after FreeNAS has written the data from the cache to the disks, nothing gets transferred. I tried this on a new zpool and also with around 1TB of data in the pool.

The problem seems to be an issue with MacOS, Windows works fine for now.

Specs client:

• MacOS 10.15.5
• 10Gbit Ethernet
• all flash

Specs FreeNAS:

• FreeNAS-11.3-U3.2 running on ESXi 6.7
• 60GB RAM allocated
• Intel Xeon E-2236
• SuperMicro X11SCH-LNF4
• SolarFlare SFP+ 10Gbit
• RAID10 using 4x WD Red 4TB
• no encryption

SMB Service auxiliary parameters:

• strict sync = no
• case sensitive = true
• server multi channel support = yes

Tunables

• net.inet.tcp.delayed ack 0
• net.inet.tcp.reass.maxqueuelen 16384