Re: What to keep in ASM?

From http://www.dbasupport.com/oracle/ora10g/ASM01.shtml :

"I/O Load Balancing. ASM is responsible for providing equal distribution of I/O loads across all available disk storage resources, so there is a measurable performance improvement. For example, ASM will split a datafile into its component extents and then spread those extents evenly across all defined disks that ASM is managing; those extents are then tracked via an indexing technique. ASM also automatically manages data via selection of desired reliability and performance characteristics instead of manually manipulating data file storage characteristics, and therefore it tends to reduce (or even eliminate) manual tuning and retuning of I/O.

A big advantage to this approach is that when ASM storage capacity changes, ASM doesn't need to re-stripe all data - it just moves enough data in proportion to the amount of added (or reduced!) storage, thus redistributing the datafile's extents evenly and keeping a balanced data load across all disks. Moreover, since ASM can accomplish the rebalancing act while the database is active, there is virtually no impact on database availability. I can also instruct ASM to increase the speed of a space rebalancing operation if I know that sufficient system resources are available, or I can tell ASM to reduce the speed of the rebalancing operation to limit the impact on the ASM I/O subsystem. "

The author of that article was also an instructor at an Oracle workshop I attended, and explained it there as well. Am I giving this feature too much credit? I haven't yet gotten to testing, I'm interested to see if those of you with active implementations have negative reviews.

Don.

On 2/26/07, fairlie rego <fairlie_r_at_yahoo.com> wrote:
> The load rebalancing of ASM is the big win in my mind.
>
> Please explain?
>
> Don Seiler <don_at_seiler.us> wrote:
> On 2/26/07, Alex Gorbachev wrote:
> > If it would be on filesystem - you might protect yourself from human
> > mistake of removing one redo log. About a year ago I remember the case
> > when DBA overwrote one copy of controlfile with small typo in tar
> > command. On the other hand, you won't be protected from "rm -f *". You
> > still can remove files from ASM but it's not that easy and it won't
> > delete file that is in use.
> >
> > In ASM - I don't see much sense to multiplex redo/controlfiles in the
> > same disk group. You might put another controlfile into your FRA
> > diskgroup, for example (you won't be able to unmount it then). I don't
> > like to rely of FRA availability but every case is different. You do
> > have disk mirroring somewhere anyway. Don't you? Mirroring on SAN or
> > ASM or at least RAID-F in the worst case.
>
> We are doing external redundancy with RAID 1+0 on the SAN. Yeah I'd
> like to have at least another copy of the controlfile somewhere. I'm
> assuming I would need the separate DG due to the fact that the
> duplication takes so long that I'd need to use the original backup DG
> while the duplication was still occuring. Worst case scenario is
> falling back to my current setup of backing up to disk and rsyncing.
>
> > ASM has nothing to do with ASSM. You can also use OMF with file system
> > just fine.
> > Just list the feature that you think you will benefit from when using
> > ASM. Then decide if it's worth the hassle of learning new technology
> > and introduce one more component into your infrastructure.
> > Note that I'm not against ASM -- we do have quite a few customers
> > using it without real problems. Real problems in this case I mean
> > corruptions. Not bad for something so new in Oracle. ;-)
>
> Yes I know that ASSM and OMF and ASM are all separate technologies, I
> was just naming other features that I want to start taking advantage
> of. The load rebalancing of ASM is the big win in my mind. Right now
> we're looking at 4 months time to really play with it before the
> production due date, so I'm more than happy to learn it.
>
> --
> Don Seiler
> http://seilerwerks.blogspot.com
> --
> http://www.freelists.org/webpage/oracle-l
>
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> Fairlie Rego
> Senior Oracle Consultant
> http://www.linkedin.com/in/fairlierego
>
> http://el-caro.blogspot.com/
> M: +61 402 792 405
>
>
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-- 
Don Seiler
http://seilerwerks.blogspot.com
--
http://www.freelists.org/webpage/oracle-l