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ASM rebalance

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younusdba
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ASM rebalance

Postby younusdba » Fri Dec 20, 2013 7:27 pm

Hi all,

what are the benefits of Rebalance in ASM when we add disks or delete disks(failure) to asm diskgroups?

if create a diskgoup

>create diskgroup dg2 disk '/dev/sdb1';

so my question here is which redundancy level the diskgoup dg2 will be created ?

thanks & regards.

Tim...
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Re: ASM rebalance

Postby Tim... » Sat Dec 21, 2013 12:34 am

Hi.

Rebalance: So lets say you add a new disk, but there is nothing on it. You are getting no benefit from the extra disk. The rebalance spreads the data across the disks, giving you the advantage of the extra spindle.

Redundancy: You've created a disk group with a single disk. It doesn't make sense for this to be anything other than external redundancy. How can it have failure groups (normal or high) with a single disk?

Cheers

Tim...
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younusdba
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Posts: 21
Joined: Mon Oct 28, 2013 5:24 pm

Re: ASM rebalance

Postby younusdba » Sat Dec 21, 2013 9:02 am

Hi Tim,
thanks for your reply, actually the above post was consist of two separate questions. below are these questions.

1)what are the benefits of Rebalance in ASM when we add disks or delete disks(failure) to asm diskgroups?

rebalance increase perfomance by spread data(extents) over all disks in a diskgroup .it is write?

2) >create diskgroup dg2 disk '/dev/sdb1';

so my question here is which redundancy level the diskgoup dg2 will be created ?

Redundancy: You've created a disk group with a single disk. It doesn't make sense for this to be anything other than external redundancy. How can it have failure groups (normal or high) with a single disk?

i am satified with your second answer. diffenately it will create a disk group with external redundancy. i have one more doubt that is if don't specify failgroup while creating diskgroup even though i mention more than one disks then will it create diskgroup with external redundancy ?

Tim...
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Re: ASM rebalance

Postby Tim... » Sat Dec 21, 2013 11:00 am

Hi.

1) Yes.

2) Well, it's a bit of a silly question. You should always be explicitly specifying the redundancy level. Not doing so it just silly. I'm not sure what the default action is exactly. The docs say, if you don't specify the fail groups and you are using normal or high redundancy, each disk will be assigned to its own failure group, but for something as important as redundancy and failure groups, not specifying explicitly what you want is insane.

Cheers

Tim...
Tim...
Oracle ACE Director
Oracle ACE of the Year 2006 - Oracle Magazine Editors Choice Awards
OakTable Member
OCP DBA 7.3, 8, 8i, 9i, 10g, 11g
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My website: http://www.oracle-base.com
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