Writing file during parity, slow write speeds?

[exdox77]

Installed my first unRaid last night and created an array. I started to transfer a file from my FreeNAS box to unRaid to test write performance. Everything was going smooth and steady and I was getting write speeds around 90MB/s, but it dropped off to 30MB/s around the for 4GB mark and it stayed there.

 

Running write tests from FreeNAS to other clients I am maxing out my gigabit LAN and the write is constant 105MB/s. 

 

Is this because the parity is running? Limited because I don't have a cache drive?

 

These tests are executed to see how long it would take my data from FreeNAS to be transferred to unRaid. But if I am getting this kind of performance after a few GB then I am not sure this is going to work. Even if I have a cache drive, what happens when the cache drive fills up?

Edited January 21, 2020 by exdox77

[JorgeB]

4 minutes ago, exdox77 said:

Is this because the parity is running?

Do you mean parity sync? It will  be slower during a parity sync, but note also that with default writing mode you'll never get gigabit speeds writing to the array, you can get them with turbo write enable.

[exdox77]

13 minutes ago, johnnie.black said:

Do you mean parity sync? It will  be slower during a parity sync, but note also that with default writing mode you'll never get gigabit speeds writing to the array, you can get them with turbo write enable.

Yes, parity sync. I have a few hours left till it is complete. I have enabled turbo write and will run the tests after the sync is complete. I do plan on getting a cache drive, but wanted to see the speed without the cache drive.

 

Being in parity sync, does that explain the sharp decrease in speed after about 3GB? 

[JorgeB]

3 minutes ago, exdox77 said:

does that explain the sharp decrease in speed after about 3GB? 

Part of it, like mentioned it will always slow down after RAM cache is full with default writing mode.