TrueNAS Scale - Better iSCSI Speeds?


I’ve been researching different ways to increase speeds for iSCSI on TrueNAS Scale. Most of my Google-Fu just shows information about TrueNAS Core or older versions.

Basic Hardware for TrueNAS Scale:

  • 2x Xeon Quad Cores
  • 64GB RAM
  • 6x 4TB Hard Drives (SAS 12gbps) in a RAID Z2 config

Currently getting about 100MB/s Reads & 140MB/s writes
ZFS cache shows about 30GB in use.

Any way to increase throughput? I was looking to see maybe adding 2x SSDs as a SLOG? Would that help at all?

Anyone else run into this issue before or something similar? How’d you fix it? Any opinions?

Have you tried setting SYNC=DISABLED for the ZVOL?

Holy crap, that increased the speeds about 60%

It might have increased the speed but, its with a cost. if your system crashes for any reason you will lose data. You are better off setting up a SSD SLOG to improve performance.

The SYNC commits are on about a 5 second cycle, so you could lose up to 5 seconds of data.