MSA20 total cache size=0

[NuMeR]

I have a problem with MSA20 I have a feeling that the cache does not work

=> ctrl all show detail
MSA20 in 0
Bus Interface: SCSI
Serial Number: P6C8C0FMQR773K
Chassis Serial Number: E038MLJ144
Cache Serial Number: P67570M9STP1QK
Chassis Name: 0
RAID 6 (ADG) Status: Enabled
Controller Status: OK
Chassis Slot: 2
Hardware Revision: A
Firmware Version: 1.24
Cache Board Present: True
Cache Status: OK
Drive Write Cache: Enabled
Total Cache Size: 0 MB
Total Cache Memory Available: 240 MB
No-Battery Write Cache: Disabled
Chassis Slot 2 Battery Info
Cache Backup Power Source: Batteries
Battery/Capacitor Count: 2
Battery/Capacitor Status: OK
Host Bus Adapter Port: 2
SATA NCQ Supported: False
Smart Array 6400 in Slot 0 (Embedded)
Bus Interface: PCI
Slot: 0
Serial Number: P57820P9SRH167
Cache Serial Number: P577A0D9SRH0YD
RAID 6 (ADG) Status: Enabled
Controller Status: OK
Hardware Revision: B
Firmware Version: 2.84
Rebuild Priority: Low
Expand Priority: Low
Surface Scan Delay: 15 secs
Surface Scan Mode: Idle
Post Prompt Timeout: 0 secs
Cache Board Present: True
Cache Status: OK
Cache Ratio: 25% Read / 75% Write
Total Cache Size: 192 MB
Total Cache Memory Available: 128 MB
No-Battery Write Cache: Disabled
Cache Backup Power Source: Batteries
Battery/Capacitor Count: 2
Battery/Capacitor Status: OK
SATA NCQ Supported: False

What can I do to make it work normally??