We got 8 HDDs in our server (Dell PowerEdge R730), combined as a RAID6 array. Yesterday evening one of the drives failed, so we are looking now for a replacement.
I've found the Seagate Exos E 10E2400 which got a 256 MB Cache and a 16 GB SSD Cache. Currently, installed are HGST Ultrastar C10K1200 with only a 64 MB cache and no SSD cache.
Would this be a problem to mix them?
The important thing for PERC controllers is to not mix SAS with SATA, or HDDs with SSDs. So no, your replacement should not be an issue.
About disk caching... for SAS disks, PERC controllers disable the on-disk cache. On Seagate drives with advanced write cache (as should be your disk), it simply means that any write issued by the controller will be cached on a portion of the NAND for write optimization. See here for more details.
