Re: Is Raid 5 really that bad for Oracle?

Please, read: http://www.baarf.com/

"joe bayer" <joebayerii(no-spam)@hotmail.com> wrote in message news:qDPOc.1753$%J6.1677_at_trndny07...
> I am quoting from Jonathan Lewis's book, Practical Oracle 8i, page 206
>
> Raid 5 has an undeservedly bad reputation as far as Oracle database
systems
> are concerned. ....
> However, for most small systems, it is almost necessary and perfectly
> acceptable; and for many large systems it is totally adequate.
> ....
> The first point is that many Oracle systems do far less writing than they
do
> reading, and the writing is usually in the backgroud anyway, so although
the
> write penalty is a notional 100%, this in=s not necessarily all that
> significant and overhead to the total I/O operation and many not impact
the
> user directly anyway.
>
> Second, although a single , small random write is likely to sustain a
heavy
> penalty, RAID 5 suppliers are aware of the issue and have taken steps to
> reduce the problem. Typically a write that fills a whole stripe does not
> need to re-creates the parity as it writes each disk. It simply discards
> and re-creates a new parity block.
>
> Third, it is beoming common practice to stick a reasonably large
> battery-backed cache on the Raid 5 device.
>
>
>
Received on Sat Jul 31 2004 - 17:59:11 CDT