19/11/10 00:30:54.79 SAzYCKM60.net
Synology SSD キャッシュ ホワイトペーパー
URLﾘﾝｸ(global.download.synology.com)
Reading and Buffering Data with SSD Cache
Once SSD Cache has been enabled, data requested from disks is continually copied and stored onto the SSD
disks. A memory map will be created in the system RAM to record which data blocks are on the SSD Cache.
Therefore SSD Cache size and system RAM size are proportionally correlated.
ということなので、再起動するとRAMのmemory map が消えるのでSSDキャッシュは使えなくなると思います。