[CentOS] write-back cache question

I have a perc5i (and perc5e) raid controller in my poweredge 2970 
running centos 5.5. The RAID controller config is set for write-back 
policy, which I can confirm by checking in OpenManage. I also called 
Dell and ran their reporting application and had them double check to 
make sure everything looks OK hardware wise and they confirm that it does

Yet when CentOS boots is appears to use the write through policy as can 
be seen below from dmesg output. Am I wrong that CentOS should query the 
RAID controller and go into the correct write mode: write-back?

hub 1-5:1.0: 4 ports detected
   Vendor: DP        Model: BACKPLANE         Rev: 1.00
   Type:   Enclosure                          ANSI SCSI revision: 05
   Vendor: DELL      Model: PERC 5/i          Rev: 1.03
   Type:   Direct-Access                      ANSI SCSI revision: 05
SCSI device sda: 2435317760 512-byte hdwr sectors (1246883 MB)
sda: Write Protect is off
sda: Mode Sense: 1f 00 00 08
SCSI device sda: drive cache: write through
SCSI device sda: 2435317760 512-byte hdwr sectors (1246883 MB)
sda: Write Protect is off
sda: Mode Sense: 1f 00 00 08
SCSI device sda: drive cache: write through
  sda: sda1 sda2 sda3
sd 0:2:0:0: Attached scsi disk sda
megasas: 0x1028:0x0015:0x1028:0x1f01: bus 16:slot 14:func 0
GSI 21 sharing vector 0x62 and IRQ 21
ACPI: PCI Interrupt 0000:10:0e.0[A] -> GSI 18 (level, low) -> IRQ 98
megasas: FW now in Ready state