slowdown after a while of copying.

[danz409]

The wall:

 

i tried reaching out to Reddit for some help on this. they have been extremely helpful but still haven't found why this comes to a near hault. at first the cache dump just simply wasn't working. (until i pulled the drives and formatted and tested them individually) the cache drive filled up and that was it. the program kept trying to fill the cache drive but since it was 95% full it slowed WAY down. i tried some suggested settings like disable parity drives until the data is moved on, as well as Tunable (md_write_method) set to reconstruct write. that seemed to have speed things up for when it was working (i also tested without the cache drives and this speed it up from ~100mbps to 240mbps) however, there is still a brick wall i hit after a while of copying. i thought it was thermal throttling, i was getting some thermal errors on my M.2 so i got a heatsink for it and it keeps it in the "orange" and no longer blasting out 60 degree warnings. when i click "move" the M.2 dumps the data to the mechanical drives pretty fast which is great because at  first it wasn't... 

pepople have mentioned that it operates at the speed of the slowest drive so i did speed tests on my drives. here are the results. 

 

 

 

I'm also including a diagnostic log. if anybody is able to help me get this going it would be much appreciated. 

 

Diagnostic log: https://drive.google.com/file/d/1FcEHWmVRFQcwyXHxUk-PCY7IrMPH1rg4/view?usp=sharing

 

Edited May 22, 2020 by danz409

[Orthos]

Since today I have two "HP NC550SFP Dual Port 10GbE Server Adapter". One in my Unraid-Server and one in my Windows 10 machine as adidional cards.

Connection works fine. Ping is without package loss and with latency of <1ms.

 

But the copy also slowdown after approx 8-10 seconds to normal (1000Mbit) network speed of 125 MB/s and stays there. It is reproducible and happens on several testet files.

Source: m.2 2500 MB/s

Target: Western Digital HDD but with SSD cache (500 MB/s)

 

I used the unraid and Windows settings as Spaceinvader One shows it here: https://www.youtube.com/watch?v=ZMMopEiwiEo

 

Anyone knows what is wrong in danz409 and or my case?

 

Kind regards and thanks for reading! Stay healthy,

Marc

[JorgeB]

11 hours ago, Orthos said:

But the copy also slowdown after approx 8-10 seconds to normal (1000Mbit) network speed of 125 MB/s and stays there. It is reproducible and happens on several testet files.

That suggests you're being limited by the device speed, not all SSDs (in fact most of them) are able to sustain nowhere near 500MB/s writes, by default Unraid uses 20% free RAM for write cache, that explains the first 8/10 seconds at max speed, then you are limited by the device actual write speed, and you can do an easy test to confirm, set the RAM cache to 40% and see if now you get approximately double the time at max speed:

 

sysctl vm.dirty_ratio=40

Type sysctl vm.dirty_ratio=20 or reboot to go back to defaults.

[Orthos]

Sorry for my very late response!

 

I don´t know why, but I have a new Cache m.2 (instead of SSD) and the speed is now continuously stable! Not full 10 gbit, but around 800MB/s (from PC m.2 to Unraid Cache m.2).

 

Thanks for your help!

[JorgeB]

22 minutes ago, Orthos said:

Thanks for your help!

You're welcome, like mentioned not all SSDs (in fact most of them) are able to sustain 500MB/s writes, 800MB/s means you now have an NVMe device, which is generally considerably faster, though like all devices some models are faster than others.

[Orthos]

Yes, both m.2 are NVMe and nevertheless it´s "only" 800 MB´s. Both should have higher speed, but I will check read/write performance of both m.2 later.

But if it will stay at "only" 800MB/s it´s fine for me, too!