I have set up a pool using 2x2TB HDDs, with an rms200 as the SLOG.
I created a ZVOL and shared it via iSCSI with sync=always set. When I connect to it from a Windows computer and copy a 100GB file, the speed initially reaches 600MB/s for the first 12GB, but then drops significantly to around 12MB/s.
Using iostat, I observed that during the first 12GB, the SLOG shows rapid writes, and the HDD has about 120MB/s writes, which is expected. However, after 12GB, the SLOG stops receiving writes, and HDD writes drop to 30MB/s, while Windows reports 12MB/s. I’ve tried adjusting the block size, but it didn’t help. When using file-based iSCSI, there’s no such issue, and it works continuously.
What could be the problem, and how can I resolve it?
I am use TrueNAS-13.0-U6.1