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ASM Diskgroup resize [message #563882] Fri, 17 August 2012 12:28 Go to next message
prashanthgs
Messages: 89
Registered: May 2005
Location: chennai
Member
Hi,

We have database with asm setup. Here the issue is

we have disks 10 for data1 and 10 for fra.

On data1 and fra (9 disks are 33gb and 1 disk is 136gb). As this 1 disk is 136 gb, we observed that striping is more on this disk which results in impacting performance of the Applications accesseing this database. Though asm keeps uniform usage across all the disks, it writes more data or reads more data from the disk which is 136gb.

How we can fix this issue like

a. Can disk of 136gb can be sliced to 33gb without any data loss?
b. Can we drop disk 136gb without any data loss?

Currently 30gb has been used on 136gb disk and 26 gb has been used on 33gb.

If you have come across this issue, how we can perform this.

Thanks

Environment : Non RAC
ASM --Oracle 11gR1
DB -- Oracle 10GR2

Re: ASM Diskgroup resize [message #563884 is a reply to message #563882] Fri, 17 August 2012 12:31 Go to previous messageGo to next message
John Watson
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Registered: January 2010
Location: Global Village
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a. No
b. Yes
Re: ASM Diskgroup resize [message #563885 is a reply to message #563882] Fri, 17 August 2012 12:34 Go to previous messageGo to next message
Michel Cadot
Messages: 67297
Registered: March 2007
Location: Nanterre, France, http://...
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a. No, you can't sliced it without first removing from the disk group
b. Yes, if ASM allows you to do it (that is remove the disk from the diskgroup which means you have enouogh space in the other disks to contain the data that are in the disk you want to remove)

If the "disks" are in fact LUN on a disk array, the io you see do not matter, you have to look at disk array level not at OS level. Are you sure you get an impact on the application because of this? How did you see that?

Regards
Michel
Re: ASM Diskgroup resize [message #563894 is a reply to message #563885] Fri, 17 August 2012 12:54 Go to previous messageGo to next message
prashanthgs
Messages: 89
Registered: May 2005
Location: chennai
Member
Thanks for your quick response.

Are you sure you get an impact on the application because of this? How did you see that?
-----------------------------------------------------------------------------------------
We see lots of long running queries in the database (espcially DML statements).
Earlier we did some gather stats, rebuilding indexes of those tables etc based on awr report. But that fixed the issue temporarily.

Then, while analyzing the disk group, we observed this also could be an cause. But as you said, disk group of 136gb was added on Nov 2011 but the performance impact issue (app support complains) only after July 2012 ie. it hit around 100 IPOS.

SAN team confirmed that IOPS (ie.measure of data coming to the disk) is more from July 2012 on this disk (136gb_ comparing to other disks. ie. it hit around 100 IOPS from July.

Re: ASM Diskgroup resize [message #563895 is a reply to message #563894] Fri, 17 August 2012 13:01 Go to previous messageGo to next message
BlackSwan
Messages: 26730
Registered: January 2009
Location: SoCal
Senior Member
http://en.wikipedia.org/wiki/Post_hoc

The change in performance may be unrelated to any observed difference in I/O activity.
where does SQL_TRACE show the actual slowdown exists?
Re: ASM Diskgroup resize [message #563901 is a reply to message #563895] Fri, 17 August 2012 13:31 Go to previous message
Michel Cadot
Messages: 67297
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
In addition, more IO on a "disk" does not mean there are served slowler than on the other "disk".

Regards
Michel
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