Hi,

 

I am running the latest version of unRAID (5.0.4).

 

After replacing my aging cache drive with a small SSD, I looked at write / read speeds directly to the cache drive and to a share which has the cache drive enabled. Both were mounted via AFP (which seemed faster than SMB on my Mac running 10.7). I used Blackmagic Disk Speed Test and found that I could get 70 / 96 MB/s write / read performance when targeting the cache drive, but only 30 / 96 MB/s write / read when targeting the cached share. I had assumed that there should not be any difference, since anything written to the share will go to the cache drive.

 

Can someone please shed some light onto this reduced write-speed behavior? I was also surprised to see that the AFP access was significantly faster than going through SMB; 32 / 49 MB/s write / read to the cache drive and 26 / 42 MB/s write / read to the cached share when mounting via SMB.

 

I'd love to hear more about how to increase the write performance. I've cranked up the MTU on the unRAID box as high as I could, and matched the Mac's MTU to that number, 6122. Both machines are connected via 1G ethernet through a switch which supports the increased frame size.

 

Thanks in advance,

Carsten

Hi,

 

I am running the latest version of unRAID (5.0.4).

 

After replacing my aging cache drive with a small SSD, I looked at write / read speeds directly to the cache drive and to a share which has the cache drive enabled. Both were mounted via AFP (which seemed faster than SMB on my Mac running 10.7). I used Blackmagic Disk Speed Test and found that I could get 70 / 96 MB/s write / read performance when targeting the cache drive, but only 30 / 96 MB/s write / read when targeting the cached share. I had assumed that there should not be any difference, since anything written to the share will go to the cache drive.

 

Can someone please shed some light onto this reduced write-speed behavior?

This has been reported on servers with very low power CPUs, e.g. Atom, AMD G.

I was also surprised to see that the AFP access was significantly faster than going through SMB; 32 / 49 MB/s write / read to the cache drive and 26 / 42 MB/s write / read to the cached share when mounting via SMB.

This is 10.7. 10.9 should not.

I'd love to hear more about how to increase the write performance. I've cranked up the MTU on the unRAID box as high as I could, and matched the Mac's MTU to that number, 6122. Both machines are connected via 1G ethernet through a switch which supports the increased frame size.

 

MTU should have no significant effect on performance, unless old or low quality networking components are used. The danger of incompatibility , misconfiguration, and reduced performance far outweighs the potential 2% gain, assuming quality components.