check web proxy cache using sata hardisk

Hi, I have a mikrobits ainos MBITSAI2 with mikrotik version 6.29.1

How can I check that the web proxy cache using sata harddisk, not the memory card ?
After 1 day uptime, the disk free in sata1 is not decreased.
Below is my proxy configuration:

[admin@MikroTik] /disk> /ip proxy print
                 enabled: yes
             src-address: ::
                    port: 8080
               anonymous: no
            parent-proxy: 0.0.0.0
       parent-proxy-port: 0
     cache-administrator: proxy_unja
          max-cache-size: unlimited
   max-cache-object-size: 256000KiB
           cache-on-disk: yes
  max-client-connections: 10000
  max-server-connections: 10000
          max-fresh-time: 4w2d
   serialize-connections: no
       always-from-cache: no
          cache-hit-dscp: 4
              cache-path: web-proxy
              
[admin@MikroTik] /disk> /disk print
 # NAME            LABEL           TYPE    DISK                 FREE       SIZE
 0 sata1                           ext3    TOSHIBA MK3...   293.2GiB   298.1GiB