RE: ASM of any significant value when switching to Direct NFS / NetApp / non-RAC?

Looks like I may have perpetrated a myth about ASM rebalancing to reduce "hot 
spots".  It appears that Oracle ASM has no "intelligent" monitoring built in to 
reduce hot spots - rather, the way extents are allocated across the logical 
volume units *helps* reduce IO hot spots, but doesn't necessarily eliminate 
them and ASM doesn't actively rebalance based on IO performance.

Chris Taylor

"Quality is never an accident; it is always the result of intelligent effort."
-- John Ruskin (English Writer 1819-1900)

Any views and/or opinions expressed herein are my own and do not necessarily 
reflect the views of Ingram Industries, its affiliates, its subsidiaries or its 
employees. 


-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of Taylor, Chris David
Sent: Wednesday, August 08, 2012 7:13 AM
To: 'dananrg@xxxxxxxxx'; 'oracle-l'
Cc: 'wts@xxxxxxxxx'
Subject: RE: ASM of any significant value when switching to Direct NFS / NetApp 
/ non-RAC?

One thing that comes to mind is the automatic rebalancing to reduce "hot spots" 
- Not sure how that works exactly in practice though.
Another thing that comes to mind is double striping (aka plaiding, 
stripe-on-stripe) - Think of a plaid shirt, you have stripes across and down - 
when striped in this manner, IO performance is really optimized - not sure how 
that relates direct NFS though.  (Make several LUNS that are physically striped 
across multiple physical disks in the storage unit, present those to the host, 
then at the host create DISK GROUPS using each LUN - stripe across the LUNS).

Here's a few links:
http://bartsjerps.wordpress.com/2011/05/25/why-oracle-asm/
http://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:30908256823200
http://h71028.www7.hp.com/enterprise/downloads/4AA0-9728ENW_ASM_EVA_Best_Practices_White_Paper_final%20121806.pdf
"The EVA configuration for OLTP testing shows an advantage toward a 
configuration that uses both ASM and EVA striping (double-striping). The 
advantages were more pronounced as the database size increased (2.5-TB RAC 
database with 1,000 concurrent users)."


Also, get with your storage vendor and discuss double striping and find out if 
they have any whitepapers discussing Oracle ASM with direct NFS.

Chris Taylor

"Quality is never an accident; it is always the result of intelligent effort."
-- John Ruskin (English Writer 1819-1900)

Any views and/or opinions expressed herein are my own and do not necessarily 
reflect the views of Ingram Industries, its affiliates, its subsidiaries or its 
employees. 


-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of Dana Nibby
Sent: Wednesday, August 08, 2012 2:34 AM
To: oracle-l
Cc: wts@xxxxxxxxx
Subject: Re: ASM of any significant value when switching to Direct NFS / NetApp 
/ non-RAC?

Thanks Wayne and Martin. We've always had striping through our SAN. And so have 
never had to use ASM for performance/fault tolerance. When you say there is 
more to ASM than striping, what functionality is that? Martin, you mentioned 
storage migration as one item. Would love to hear more details and use cases 
for non-overlapping ASM functionality (non-overlapping with NetApp RAID DP 
appliance storage with DNFS). 

Without ASM, I understand there's one less piece for the sysadmins/storage 
admins to manage. And so it reduces complexity. But I want to be sure removing 
ASM does not cause any loss in our ability to rapidly respond to customers. 
Given the separation of duties in our organization and the workload of the 
sysadmins/storage admins, this is key. The bottom line: would removing ASM make 
the customer less happy, more happy, or would the change likely be 100% 
transparent? Will we DBAs have to rely more upon our sysadmins / storage admins 
to get things done, e.g. add and grow datafiles, etc? If so, customer service 
will by definition suffer. Because that's one more layer to go through to get 
things done.


Another issue: if we rebuild all our instances without ASM, can we still take 
advantage of Oracle Restart? In other words, do we continue to perform Grid 
Infrastructure installs and then just ignore / not configure an ASM instance? 
Perhaps it's better for another post, but are there reasons *not* to use Oracle 
Restart for non-RAC 11g instances?


Since I imagine most shops use RAID storage (and increasingly sophisticated 
SAN/NAS devices), how popular is ASM? Oracle still seems to tout ASM as a Best 
Practice. But a best practice for whom and in what context(s)? For those using 
JBOD? Maybe I'm thinking of Oracle literature back from 10g or the 1st release 
of 11g. If ASM isn't on the path to deprecation in today's storage landscape, 
why not?



________________________________
 From: Wayne Smith <wts@xxxxxxxxx>
To: oracle-l <oracle-l@xxxxxxxxxxxxx>
Sent: Tuesday, August 7, 2012 1:34 PM
Subject: Re: ASM of any significant value when switching to Direct NFS / NetApp 
/ non-RAC?
 
If you are moving from unstriped/non-raid disk to a disk appliance, that 
probably means ASM striping support is of no interest going forward, but their 
is more to ASM than that.

That said, I believe ASM is an unnecessary complication for my 
standalone/non-RAC databases.  Your mileage will vary.
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