Add 'detail' to the command below for more detail.

# hpssacli controller slot=1 show config

Smart Array P222 in Slot 1                (sn: PDSXH0BRH6E0ZP)

   array A (SAS, Unused Space: 0  MB)


      logicaldrive 1 (558.7 GB, RAID 1+0, OK)

      physicaldrive 2I:1:1 (port 2I:box 1:bay 1, SAS, 300 GB, OK)
      physicaldrive 2I:1:2 (port 2I:box 1:bay 2, SAS, 300 GB, OK)
      physicaldrive 2I:1:3 (port 2I:box 1:bay 3, SAS, 300 GB, OK)
      physicaldrive 2I:1:4 (port 2I:box 1:bay 4, SAS, 300 GB, OK)

   SEP (Vendor ID PMCSIERA, Model SRCv8x6G) 380 (WWID: 50014380305FB0DF)

# hpssacli controller slot=1 show status

Smart Array P222 in Slot 1
   Controller Status: OK
   Cache Status: OK
   Battery/Capacitor Status: OK

CAUTION: Because physical drive write cache is not battery-backed, you could lose data if a power failure occurs during a write process. To minimize this possibility, use a backup power supply“

• First get current cache status:

  # hpssacli controller slot=1 show config detail |grep -i cache
     Cache Serial Number: PBKUA0BRH6E54G
     Wait for Cache Room: Disabled
     Cache Board Present: True
     Cache Status: OK
     Cache Ratio: 25% Read / 75% Write
     Drive Write Cache: Disabled
     Total Cache Size: 512 MB
     Total Cache Memory Available: 304 MB
     No-Battery Write Cache: Disabled
     Cache Backup Power Source: Capacitors
     Cache Module Temperature (C): 35

• Enable drive write cache:

  # hpssacli controller slot=1 modify dwc=enable
  
  Warning: Without the proper safety precautions, use of write cache on physical 
           drives could cause data loss in the event of power failure.  To ensure
           data is properly protected, use redundant power supplies and
           Uninterruptible Power Supplies. Also, if you have multiple storage
           enclosures, all data should be mirrored across them. Use of this
           feature is not recommended unless these precautions are followed.
           Continue? (y/n)