Re: Data Mirroring on two data centers -- How to use ASM ?

  • From: "Alex Gorbachev" <gorbyx@xxxxxxxxx>
  • To: db.mail.1@xxxxxxxxx
  • Date: Thu, 18 May 2006 22:19:23 +0200


Coincidently, I just published what I learned today on managing large
storage capacity with ASM - You might
find it interesting.

For ASM devices you should be able to use deither LUNs from your
storage boxes or AIX's volume manager (if this colume manager is
cluster aware). At least on Linux I was able to configure it with both
raw devices and LVM2 volumes (even though it's not clustered VM and
not supported in this way). However, I don't see the benefit of using
both - normal volume manager and ASM - choose one. Otherwise, you will
have overhead of administration and more problems as more layers used.

Striping cannot be disabled in ASM. Mirroring can be external - yes.

Btw, you can even use files as your asm disks if you set
_asm_allow_only_raw_disks=false. Though, this is probably not a good
idea for production but nice feature to play at home and use files
instead of partitioning you hard drive.

2006/5/18, Madhu V <db.mail.1@xxxxxxxxx>:

Thank You both !!


 Unfortunately, I am dealing w/ AIX here (although I would prefer Linux).
Idea here is to mirror data across TWO data centers while using ASM. In this
particular test we won't be using GPFS (CFS). Most of the documentation out
there refers mainly to raw devices. So I am under the impression that, use
AIX volume manager to deal with the LUNS mirrored across two data centers
and all i need is simple raw devices and ownership changed to Oracle:dba to
be able to use by ASM (external redundancy). So if i am correct, we are
using AIX volume manager along w/ ASM (external redundancy)... Please
correct me if i am wrong

 Secondly, i think this should be another possibility... assign the LUNS
(from both the data centers) to ASM instance and create failure groups to
mirror the data across two data centers... but we will have to careful in
choosing the LUNS for each failure group to make sure the data is mirrored.
In this scenario, there is no use of AIX volume manager, but ASM will mirror
the data.. again please correct me if i am wrong w/ advises.

 if at all, the above are possible, which is one is best and why?


 Dick, would you please confirm turning off striping , I am under the
impression that Mirroring can be external, but ASM does striping and no way
to stop it.

 Thank You,

 Goulet, Dick wrote:


    I'm not sure if you can use AIX Volume manager with ASM.  I doubt it.  I
did my RAC install on RedHat so used the Oracle cluster software, cluster
ready services I believe it is called.  It installed very nicely so I would
want to do the same thing next time as well.  As for striping, if you don't
want ASM to do the striping for you, like I did not, you can choose to have
that managed externally.  It's a simple check box in the installer.

-- Best regards, Alex Gorbachev

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