configuration choices with Dell CERC (adaptec 2610SA)

[Scott Long]

user wrote:

> 
> On Sat, 26 Nov 2005, Herve Boulouis wrote:
> 
> 
>>Le 26/11/2005  14:17, user a �crit:
>>
>>>Read caching: yes/no (default is yes)
>>>
>>>(read caching does not rely on a battery, and is completely "safe",
>>>right?  I am going to set this to "yes", however I wonder - why would
>>>anyone _ever_ set it to "no" ?)
>>
>> 
>>You usually want to disable read caching on all aac based adaptec raid
>>controllers because it decreases performance.
>>
>>
>>>Write caching: enable/disable
>>>
>>>(this is the one that can get you into trouble if the system loses power
>>>before a write is committed to disk, and the battery is dead, right?  I am
>>>going to set this to "disable" because I do not think the 2610SA has a
>>>battery ... right ?)
>>
>>If your server is plugged on a UPS you can safely enable it, it's quite
>>a performance gain.
> 
> 
> 
> One other clarification - I have the option to turn write caching on and
> off when I create the array (I am turning it ON now for the array based on
> your opinion) ... but I also have an option in the adaptec bios to turn
> write-caching on for each specific disk drive.  I have also turned this
> on.
> 
> Are these seperate settings, or are they redundant ?  (or does write
> caching for the array _depend on_ having write caching for each drive
> turned on ?)
> 
> thanks.
> 

These are searate settings.  The drive has a cache, and the controller
has a cache.  If you enable the drive cache, you really should have a
UPS and a good data archive plan in place.  Until a few years ago
Adaptec did not enable the drive cache by default and did not recommend
enabling it.  Times have changed, though, but not for very good reasons.
Only enable this option if you don't actually care about your data.

Scott