Re: ASM and RAID

On Mon, 15 Dec 2008 21:03:53 -0600, Michael Austin <maustin_at_firstdbasource.com> wrote:

>Now that we have sufficiently beat the RAID5 horse to death, let's add a
>twist to the debate. What is your experience either in the lab or real
>sites where you have the virtualization at the array level (pick your
>RAID level) in addition to the virtualization provided by ASM in an
>Oracle eBusiness environment.
>
>Let's say you have Tier1 storage (high end whatever...) you have 50
>spindles in a RAID0+1 providing ~12.5TB of raw storage that we carve out
>100 50GB LUNS and present them to our ASM environment. How, in your
>testing and research, does performance either improve or suffer with the
>addition of ASM. The database is scattered across 6 separate disk
>groups with logfiles etc in their own disk group.

While not being a very large database shop, all I can say about ASM on top of RAID is that it uses extra CPU, but makes DBA life a bit easier (no need to specify datafile names and easier to create new instances, for example). We are using IBM DS4000 series SAN with RAID10 LUNs presented (through VIO server) to AIX/Linux LPARs on a pSeries 570. AIX LPARs are using direct access to raw devices by Oracle 9iR2 processes, while Oracle 10gR2 on Linux uses ASM. If we look at 'sar' output - we can hardly notice the overhead (our CPUs are 1.65GHz POWER5), while looking at nmon/topas screens during data loads or queries we can see ASM processes taking some 7-10% of CPU at peak times. Did not encounter any reliability matters so far.
We are about to install a new p570-MMA and I will be definitely going with ASM on AIX LPARs as well.

On the RAID5 matter - I do not see anything terminally wrong with RAID5 even after reading the whole thread, but we only use RAID5 LUNs for disk backups.

Alex Received on Wed Dec 17 2008 - 03:11:26 CST