[CentOS] write-back cache question

[James Chase]

Can anyone with write-back cache working just confirm that they see some 
sort of indication of write-back in dmesg?

As I mentioned I talked with Dell and they claim it is working, however 
I spoke with VMWare and they said if it isn't indicated in dmesg, then 
it isn't working. It would just be good to know it is indicated as 
functional in this way for others so I can have something to go on with 
Dell.

On 2/11/2011 10:00 AM, James Chase wrote:
> 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
>
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