Hello -

 

I've been reading a bunch of old threads about some of the tunable settings, specifically lots of recommendations for Tunable (md_num_stripes) to be set to 4096 for systems with sufficient ram. I can't find anything recent on the topic, and the default value is 1280 on my system. I have plenty of ram (currently use around 10gb of my 32gb). Should I increase this? Is there any documentation around this Tunable setting or the others listed? I can't find it in the manual. Screenshot attached. Thanks.

 

 

There has been a lot of discussion in older threads regarding the Tunable (md_num_stripes) setting, with many recommending increasing it to 4096 for systems with sufficient RAM. However, recent official guidance on this setting is somewhat limited.

 

From what I understand, md_num_stripes controls the number of memory buffers allocated for parity and data disk operations. Increasing this value can improve performance, especially for high-bandwidth workloads, by reducing disk I/O contention. Since your system has 32GB of RAM and is only utilizing ~10GB, you likely have room to increase this value.

 

Should You Increase md_num_stripes?

-If your system experiences slow parity checks, disk write slowdowns, or frequent disk I/O bottlenecks, increasing md_num_stripes could help.

-Many users have reported performance improvements by setting this to 4096, but results may vary based on workload and hardware.

-Keep in mind that each additional stripe consumes memory, so monitor your RAM usage after making changes.

 

Other Related Tunables:

-md_queue_limit: Controls the maximum number of queued operations per disk. A higher value can improve parallel disk operations but may not always translate to real-world gains.

-md_sync_limit: Defines the number of sync operations Unraid can run in parallel. Increasing this might speed up parity syncs and rebuilds but could also increase disk contention.

-md_write_method: "Auto" will default to reconstruct write (turbo write) if conditions allow, which can significantly improve write speeds at the cost of spinning up all disks.

 

Next Steps:

-If you want to experiment, try increasing md_num_stripes to 4096, then test parity checks and large file transfers to see if performance improves.

-Monitor your RAM usage to ensure there are no unintended memory constraints.

-If you encounter instability, revert to the default 1280 and test again.

 

For official Unraid documentation, these tunables are not extensively covered in the manual, but you may find discussions on the Unraid forums or through user benchmarks (when I was looking into it way back ago there was an awesome dude on Reddit that explained it very well in depth, ill try to dig that up). Hope this helps and sheds some more light on the topic! If you’re looking for deeper insights, digging through some of the older, outdated Reddit posts and older Official Unraid forum threads might provide additional clarity.

I tried to explain that the best I could, but it had been a while. If I can explain it any better or give any more info just let me know!

 

Best & Success

-DirtyDarrell