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AIX v5.3 I/O problem ???

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  #1  
Old June 5th, 2008
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I/O problem ???
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I need help on a possible performance problem. We have a p560 running AIX v5.3 8 cpu/32gb mem with 2 fiber cards that is running Oracle 10g. Disk I/O is heavy during certain times but from iostat and vmstat output, I don't think there is alot we could do to help performance with
such heavy I/O occurring. Not seeing any paging to page space but seeing heavy paging to file system (via nmon). Attached is a vmstat of what we typical see.

Thanks,

Danny
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File Type: txt vmstat_1.txt (1.0 KB, 4 views)
Last edited by DANNYC; June 6th, 2008 at 09:39.
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  #2  
Old June 6th, 2008
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Re: I/O problem ???
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Except for the I/O waits everything looks pretty normal. The I/O waits are not necessarily cause by disk I/O, they could be Network I/O or waiting for another process to complete.

How are your disks set up in this environment? Direct attached Fibre, Local SCSI, Virtual I/O?

How much CPU and how many virtual CPUs do you have?

What are your vmo settings, as that may shed some light on what it is doing?
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That said anything I say here is my own opinion and not anything that you can ever hold against IBM.
Ohhh and don't forget that I make mistakes too....
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Old June 6th, 2008
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Re: I/O problem ???
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Thanks for the reply Ross. We are attached to ds6800 disk via our SAN.
The is an 8cpu server with SMT turned on so 16 logical processors.

These vmo setttings are the only ones I changed:
MINPERM%=3
MAXPERM%=90
MAXCLIENT%=90
lru_file_repage=0

AIO is also turned on.
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Old June 6th, 2008
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Re: I/O problem ???
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what you'll need to do is to find out which files are being written and see if you can split them off into different SAN LUNs that is probably the only thing you'll be able to do to help.

That sort of analysis is not something I can help you with online. You'll need to use filemon to work out what is going on.
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Ohhh and don't forget that I make mistakes too....
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Old June 6th, 2008
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Re: I/O problem ???
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WE truly think the problem is with the way the application manipulating the tables (many full tables scans) in Oracle. Anyway, as always Ross, thanks for your assistance.
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Old June 6th, 2008
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Re: I/O problem ???
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If your Oracle datbase is in filesystem space have you checked the Oracle documentation about using the CIO/DIO filesystem mount option.
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Old June 6th, 2008
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Re: I/O problem ???
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The dbf's are mounted with Concurrent I/O turned on. Thanks for the reply.
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Old June 7th, 2008
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Re: I/O problem ???
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You are correct though that most I/O problems like this with Oracle are caused by the programming at an Oracle level rather than anything else.

But it never hurts to have back up when talking to your DBAs :-).....
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That said anything I say here is my own opinion and not anything that you can ever hold against IBM.
Ohhh and don't forget that I make mistakes too....
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