Is Write back cache enabled on physical disks of Perc 6/i ?

Christian Rishøj christian at jetment.com
Thu Mar 26 10:32:24 CDT 2009


On 26 Mar 2009, at 16:15, Dushyanth wrote:

> Christian Rishøj <christian <at> jetment.com> writes:
>>
>> On 26 Mar 2009, at 11:32, Dushyanth wrote:
>>
>>>> Any pointers/suggestions would be of great help.
>>>
>>> Does anyone know if write back cache is enabled on the physical
>>> disks of
>>> Perc 6/I controllers ?
>>
>> Our server came from Dell with disk caches disabled. We saw a small
>> performance gain by enabling it ourselves.
>>
>> You can inspect the configuration with omreport. E.g.:
>>
>> $ sudo omreport storage vdisk
>> List of Virtual Disks in the System
>
> The virtual disk status (raid array) shows write back status. Mine  
> does too.
> Each hard disk in that raid array also has cache (disk cache). The  
> physical
> disks status of the virtual disk does not confirm whether those disk  
> caches are
> disabled (check below).

You are right. The cache policy from the vdisk command relates to the  
controller cache, not on-disk caches:

http://support.dell.com/support/edocs/software/svradmin/5.1/en/omss_ug/html/cntrls.html#681570

Christian



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