Re: Cache battery and Raid Controller Design WAS: Re: Rép. : Question of a Newbie to POWER Systems

Exactly. The cache battery is supposed to support the cache across power
loss events, not to flush the cache before the drives spin down. This is
especially necessary since the drives may be in a different frame (with
different power supply) than the RAID controller.

On Wed, Mar 30, 2011 at 9:56 AM, Chris Bipes <chris.bipes@xxxxxxxxxxxxxxx>wrote:

But if the Cache is kept live on the controller, when you power the system
back on, the controller will write the contents of the cache to disk, as the
disks are now powered up and spinning. This happens before you actually
start the OS, well the partitions at least. It is done is Hardware/Firmware
on the RAID controller, regardless of the OS being loaded.

--
Chris Bipes
Director of Information Services


-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:
midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of sjl
Sent: Wednesday, March 30, 2011 7:31 AM
To: midrange-l@xxxxxxxxxxxx
Subject: Re: Cache battery and Raid Controller Design WAS: Re: Rép. :
Question of a Newbie to POWER Systems

But if the system loses power, will not also will the disk drives attached
to that RAID controller lose power? At that point, it seems irrelevant to
me to have a battery backup on the RAID controller to keep the data cached
without a way of also powering the disk to allow the data to be written to
storage...
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