Re: Setting up storage Array for ASM
- From: David Robillard <david.robillard@xxxxxxxxx>
- To: Steven Andrew <postora@xxxxxxxxx>
- Date: Fri, 22 Apr 2011 07:53:14 -0400
Hello Steven,
> We are building up a system from scratch and wanted to follow the best
> practices in setting up SAN Storage Array for ASM. With 22 disks in the
> array for use, i was planning on doing 11 + 11 in Raid 1/0 setup with
> maximum stripe possible within the array and carve out 3 x 2G LUNs for
> vote_ocr and 2 x 1TB LUNs for both DATA and FRA diskgroup. vote-ocr DGs
> will use normal redundancy and database in external redundancy.
You might want to read the fine manual on ASM. You don't specify which
database version nor the OS you plan to use. So I'll assume you're
going with 11gR2. If so, check out « Oracle ASM Administrator's Guide
11gR2 Chapter 2: Considerations for Oracle ASM Storage,
Recommendations for Storage Preparation » [1].
This official documentation says that « A minimum of four LUNs (Oracle
ASM disks) of equal size and performance is recommended for each disk
group. » and that you should « Create external redundancy disk groups
when using high-end storage arrays. »
With that in mind, you might want to change the 2 x 1 TB LUNs for 4 x
512 GB LUNs. But keep in mind that if you need to add more disk space
to either disk groups, you will need a 512 GB LUN which is relatively
big. That is to satisfy the ASM data distribution and balance
operation as the fine manual says: « Oracle ASM data distribution
policy is capacity-based. Ensure that Oracle ASM disks in a disk group
have the same capacity to maintain balance. » In other words, use LUNs
of the same size in the same disk group.
Also, if you plan to use your +FRA disk group as your RMAN backup
area, consider giving your +FRA disk group more disk space than the
+DATA disk group. Especially if you plan to use RMAN incrementally
updated backups [5]. The well named Doc ID 762934.1 « Flash Recovery
Area Sizing » can help you with, well, sizing the +FRA. This one is
also interesting: Doc ID 305648.1 « What is a Flash Recovery Area and
how to configure it ? ».
You might also be interested in Doc ID 1187723.1 « Master Note for
Automatic Storage Management (ASM) » along with Doc ID 265633.1 « ASM
Technical Best Practices » which is for 10gR2 and 11gR1. the « Top 10
Things You Always Wanted to Know About ASM But Were Afraid to Ask » by
Nitin Vengurlekar [2] which is quite interesting.
Finally, a side note on ASMLib. The official ASM documentation [1]
says that if you're running Linux, then « use the Oracle ASMLIB
feature to provide consistent device naming and permission
persistency. ». IMHO this is a bad idea as you can achieve the same
goal with udev instead of ASMLib [3]. But don't take my word for it
and check out Christo Kutrovsky's presentation « RAC+ASM: 3 years in
production. Stories to share » [4].
Regards,
David
[1]
http://download.oracle.com/docs/cd/E11882_01/server.112/e16102/asmprepare.htm#BABJHHEC
[2]
http://www.dbaexpert.com/blog/wp-content/uploads/2009/08/doug-top-10-asm-questions.pdf
[3]
http://itdavid.blogspot.com/2011/03/how-to-increase-disk-space-in-existing.html
[4]
http://www.pythian.com/news/9055/oracle-rac-asm-3-years-in-production-stories-to-share-slides-from-rmoug10/
[5]
http://download.oracle.com/docs/cd/E11882_01/backup.112/e10642/rcmbckba.htm#CHDEHBFF
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