Re: More than 2 ASM Diskgroups in a RAC Enviornment with 2 Databases

  • From: Greg Rahn <greg@xxxxxxxxxxxxxxxxxx>
  • To: ade.turner@xxxxxxxxx
  • Date: Thu, 08 Mar 2007 20:16:17 -0800

With the mindset that ASM is a volume manager, there is no inherent performance advantage (or disadvantage) to having more than one diskgroup. For example (and please, no criticism of the benchmark...) Oracle has a TPC-H 10TB scale factor benchmark with ASM and one single ASM diskgroup was used. See the FDR here:

I personally have used a single ASM diskgroup of 444 x 256GB physical spindles spanning 37 arrays in an 8 node RAC cluster. Flash recovery was not needed in this case.

The important thing to keep in mind is how the LUNs are carved up from the storage and how the ASM diskgroups are implemented. Be mindful if the same physical spindles participate in more than one diskgroup, a busy diskgroup can negatively impact other diskgroups who share those same spindles. You may want to choose separate "groups" of disks for the diskgroups so that they are isolated from each other. This may assist you later in troubleshooting disk related performance issues.


Greg Rahn

-------- Original Message --------
Subject: Re:More than 2 ASM Diskgroups in a RAC Enviornment with 2 Databases
From: Adrian <ade.turner@xxxxxxxxx>
To: kaygopal@xxxxxxxxx, naqimirza@xxxxxxxxx, "'Oracle-l List'" <oracle-l@xxxxxxxxxxxxx>
Date: 3/8/2007 11:05 AM
Hi Gopal,

I believe the intention of the WP is that the S.A.M.E. methodology is
The more disk groups the less disks would be striped and mirrored within
each one, implying worse performance.

My understanding is that unless you are in the terabyte++ area there is no
reason to have more than one disk group for data and one for flash recovery.


-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of K Gopalakrishnan
Sent: 08 March 2007 16:13
To: naqimirza@xxxxxxxxx; Oracle-l List
Cc: racdba@xxxxxxxxxxxxx
Subject: Re: More than 2 ASM Diskgroups in a RAC Enviornment with 2


Which document you are talking about? We never say 'no more than 2
disk groups per cluster'.

Btw your initial plan seems perfect.


On 3/7/07, Naqi Mirza <naqimirza@xxxxxxxxx> wrote:
I see a similar question to this has already been posted, but just
if anyone's actually had to configure something like this before.

----- Original Message ----
From: Naqi Mirza <naqimirza@xxxxxxxxx>
To: oracle-l <oracle-l@xxxxxxxxxxxxx>
Sent: Wednesday, 7 March, 2007 2:07:47 PM
Subject: More than 2 ASM Diskgroups in a RAC Enviornment with 2 Databases


---- Start ----
Config Details:

2 Node 10gR2 RAC
HP-UX (PA-RISC) 64 Bit, 11.23
Serviceguard 11.17
ASM used as storage option for database and recovery files.

---- End ----

This 2 node cluster will host 2 RAC databases. Looking at the best
document for ASM, I see it says that typically you should have no more
2 diskgroups per RAC cluster.
However, the initial plan was to create 4 diskgroups - 2 for each
Just wondering if anyone has done something similar to this, or if anyone
has more than 1 rac database using asm as the storage?




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