Re: The Age Old Unclearly Answered Question: Write-Through or Write-Back

"El Toro" <medawsonjr_at_yahoo.com> wrote in message news:2e1cd2b.0309171459.89ace69_at_posting.google.com...
> We're going to a new colo facility where they have all their clients
> using Sun StorEdge T3s for database backend. These things have a
> 1Gbps FC (100MB/s) interface, with 1GB of battery-backed write-cache.
> It also has hardware RAID.

<snip>

> Now, they're trying to say that we need the write cache for
> performance. I recall reading that, with my type of workload, Oracle
> would be better off with more investment in host RAM and optimal disk
> striping than disk write cache. I can't remember where I read this
> online, though.
>
> Does anyone have any URLs, preferably from Oracle, that explains this?
> It would be very helpful to have for a meeting scheduled tomorrow
> morning with the colo facility. I already have docs about the HW RAID
> vs. SW RAID myth.

Check out James Morle's Sane San paper available at (amongst other places www.baarf.com). In particular he makes the (possibly a bit overstated) suggestion that you might as well ignore the cache since the SGA is going to soak up most of your IO that is amenable to caching anyway.

-- 
Niall Litchfield
Oracle DBA
Audit Commission UK