High latency spikes every minute / ESXi 6.7 U1 / HDD RAID + SSD Cache

Hi there,

We're owning an esxi 6.7 on a small ProLiant DL360 Gen9 with an internal Storage and SSD Cache.

I checked the esxi perfomance tabs and noticed that there is a huge latency spike every minute (light blue graph).

What could cause this spikes? Is this the moment were the SSD Cache empty itself to the HDD Raid?

Regards,

Jonny