Re: Extremely Slow Database Import Due to Disk Cache?
From: Will Greene (willgreene99_at_hotmail.com)
Date: 06/23/03
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Date: Mon, 23 Jun 2003 10:50:26 -0500
Thank you for the information.
Will
"Elias" <nospam@charter.net> wrote in message
news:vf77moi29fle39@corp.supernews.com...
> Will Greene wrote:
> > Hello,
> > I am having an extremely long processing time for a small oracle
> > database to import. I am running on a SunE450 with 2 cpu's at 300Mhz and
2
> > channel raid 5. The import file is only 2.5Gbs and should normally
require
> > only 2-3 hours to import.
> >
> > When I bring up the config for the DPT controller, I get an error
message of
> > "Cache is in Write-Through Mode because ... or battery is in Maintenance
> > Mode".
> > Click [Ok] and the battery status says "initial configuration discharge"
or
> > somesuch.
> > Any idea of what's going on? Could this be the culprit why disk i/o taks
> > take sooooo long?
> >
> > Thanks,
> > Will
>
> Yes the cache mode is causing slow performance. Using write-through
> sends all data straight through the cache immediately to disk. Your
> DPT/Adaptec system is a type of storage that uses its battery to keep
> the data in cache during a power outage, then write to disk once the
> power comes back on. The other type (that yours is not) uses the
> battery to write the uncommitted cached data to disk then powers down.
>
> If you were to have a power outage with a drained, malfunctioning, or
> expired battery the system might not have enough battery power to out
> last a power outage. If you loose battery power during an outage then
> the uncommitted data is lost forever. So, write-through protects you
> from this scenario.
>
> Your battery will from time to time discharge and recharge itself as
> part of a regular preventative maintenance cycle. Assuming everything
> is ok with the battery when it comes back to full charge the array
> should set the cache back to write-back mode. I'm pretty sure this is
> what will happen with your array. So, just give it about 12 hours or so.
>
> Elias
>
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