[6.8.3] What might have caused this bottleneck?


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On the NAS in my signature I came across a bottleneck today and I am interested in knowing what might have caused it.

 

This is a lightweight NAS that serves one PLEX Docker and also acts as an on-site backup for my desktop PC. My wife was watching a movie that was already encoded correctly for the Apple TV and without thinking I decided to back up a large number of small files to the backup share while the movie was playing. Very quickly the movie started to stutter then froze until the file transfer was complete.

 

The movie was streaming from one of the HDDs. I know from experience that Plex only causes the i3-8300 to go between 10% and 25% load as a chunk is requested.

 

The file transfer was 4Gb in size with about 8500 small files. It was going to the Backup share which is Cache = Yes via FTP (FileZilla). The Source files were on my desktop NVME drive and went over Cat6 LAN through a 1Gb switch. The NAS cache drives are a pair of SSDs which are on the motherboard's SATA connectors. The HDDs go through the SAS9207-8i card.

 

When I heard that the movie was stuttering I looked at the Dashboard and saw the CPU with a couple of cores pegged at 100% and the other two at about 80%. I also wondered if I might have saturated the motherboard's SATA lanes.

 

Since it is only a 4-core CPU I do not have any core pinning.

 

What do you think might have caused the bottleneck and what might I be able to do so that it is less likely to happen again?

Edited by DanielCoffey
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