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, 20206 yr by exdox77

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.

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? 

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.