Purpose of battery in perc5/i controller

[Radim Hejc]

But, IMHO, it will work correctly only when your harddrive write cache 
is disabled, which will slow down the disks.
(there is up to 32MB of HDD's cache and when power goes down, cached 
data will be lost)

Correct me if  i'm wrong


Radim H.

Radim Hejc(
IT infrastructure
U-TURN, a.s.
Argentinská 38/286
17000 Praha 7, Czech rep.



Tino Schwarze napsal(a):
> On Sat, Mar 01, 2008 at 03:00:06AM -0500, Dmitriy Beloslyudtsev wrote:
>   
>> What is the purpose of battery in perc5/i scsi raid controller? Let's
>> imagine we have a write cache in write-back mode and during disk write
>> operation we lost the power. If the battery is needed to flush the cache
>> content to the physical disks during this power outage, who will produce the
>> power to spin the physical disks in internal bays of pe2950? Am I missing
>> some key concept in here?
>>     
>
> The battery will only buffer the controller's RAM. So next time the
> system boots up, the controller will remember that there's still
> something to write to disk and it will do so.
>
> HTH,
>
> Tino.
>
>   
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