RE: New 270.

["Andy Nolen-Parkhouse" <aparkhouse@xxxxxxxxx>]

Steve,

When the 'write' is put in the cache, the OS is notified that the
operation is complete and the program can move on to its next operation.

I don't know specifics on the controllers we've been referencing in this
thread, but IBM states that their controllers will either have
non-volatile memory or a battery on the controller to maintain the
information.  The physical writes to disk would then occur when power
was restored to the drives.

The following link gives more depth:
http://www-1.ibm.com/servers/eserver/iseries/whpapr/integrated_storage.h
tml#nonvolatile%20fast-write%20cache

Regards,
Andy Nolen-Parkhouse


> -----Original Message-----
> From: midrange-l-admin@midrange.com
[mailto:midrange-l-admin@midrange.com]
> On Behalf Of Steve Richter
> Sent: Thursday, June 06, 2002 8:13 AM
> To: midrange-l@midrange.com
> Subject: RE: New 270.
>
> I am curious to know how a disk controller with a write cache handles
a
> power loss.  Does os400 consider a write to the controller ( the cache
) a
> write to the disk ? When you loose power is the cache wiped out immed
> resulting in database corruption?
>
> Does the controller or disk have a built in battery backup that keeps
the
> disk spinning long enough when power is lost to write the cache to
disk ?
> Will a controller with a very large write cache always be able to
ensure
> that the data is written to disk ?
>
> Steve Richter