I saw a topic talking about this with 4 cache drives. I only have a single cache drive. Even before I had no cache drive and a different CPU and motherboard I've always had this problem. I've tried adjusting the tunables. No matter what I do I still get these kind of "freezes".

 

It often manifests itself when Sonarr is unpacking a download. Everything else seems to freeze until it's done unpacking the file. I can also trigger it by copying large files between array drives.

 

This happened before and after I had a cache drive and also when I had an older dual Xeon system and now with my i5 3470.

 

I have an IBM M1015 that's been cross flashed to IT mode. My cache drive and parity drive are on my motherboard's 2 6Gb connectors and the rest of the 8 are on the SAS controller.

 

The only common factor besides the drives themselves has been the SAS card but I've tried swapping out for 2 2-port SATA cards and using all the 3Gb ports on the motherboard and it still happens.

 

This doesn't happen that often but it is frustrating when it does happen.

Edited July 27, 20187 yr by Taddeusz

I am not absolutely sure, but mine has some issues with a Raid-0 NVME cache on mine... I always just assumed it was an issue with filling up the write buffer, and all commands having the same priority level, so sometimes QEMU/KVM has to pause parts of the VM till it gets write access back to prevent corrupting things...

 

Bottom line, you can choose between being space efficient by sharing the drive, or to really remove this issue, remove it from being a cache drive, and instead pass it through exclusively to the VM...

I use mostly Docker based applications and even those get preempted. I realize unRAID is primarily for storage and it kind of feels like it prioritizes array and cache over anything else. Like with Sonarr further downloads still happen while its unpacking the previous one but download performance is greatly diminished. So it’s not a complete freeze but it’s definitely favoring drive access over everything else.