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тАО04-25-2005 04:19 PM
тАО04-25-2005 04:19 PM
All volumes are mirrored with the exception of the swap volume. There is no paging occuring.
I have attached the output from sar -d.
Any ideas as to why this is?
Thanks
John Leavens
Solved! Go to Solution.
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тАО04-25-2005 04:26 PM
тАО04-25-2005 04:26 PM
Re: Mirror UX performance issue
If they are the same. Where are they on the scsi chain?
If you mirror across unlike disks you can cause performance issues.
You might also want to make sure that cables and terminations are good on the disk giving you trouble.
SEP
Owner of ISN Corporation
http://isnamerica.com
http://hpuxconsulting.com
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com
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тАО04-25-2005 05:24 PM
тАО04-25-2005 05:24 PM
Re: Mirror UX performance issue
If your swap volume goes bad you system is dead. Sure there are no data to preserve on the swap area. But you need the redundancy in case of a disk failure.
Do you see you problem during read or write (or both)?
How is you schedule set up(parallel or sequential)?
Is mirror_write_cache on or off?
Regards,
Trond
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тАО04-25-2005 05:29 PM
тАО04-25-2005 05:29 PM
Re: Mirror UX performance issue
They on the internal Ultra160 controllers.
They may be on different controllers, though.
Is there some way to tell where they are in the scsi chain from the hardware path?
See the attached ioscan.
Thanks,
John Leavens
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тАО04-25-2005 05:39 PM
тАО04-25-2005 05:39 PM
Re: Mirror UX performance issue
I suggest cstm, mstm or xstm and do a full check on the hardware.
I've heard varying opinions about mirroring swap. I did it in my last position and on my personal systems, but others believe its a bad idea.
I'd look for some kind of hardware issue causing this.
SEP
Owner of ISN Corporation
http://isnamerica.com
http://hpuxconsulting.com
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com
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тАО04-25-2005 05:45 PM
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тАО04-25-2005 05:51 PM
тАО04-25-2005 05:51 PM
Re: Mirror UX performance issue
Thanks for the feedback on the swap.
The scheduling policy is set to parallel.
Write Cache is set on.
Mirror Consistency is set off.
John Leavens
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тАО04-25-2005 06:43 PM
тАО04-25-2005 06:43 PM
Re: Mirror UX performance issue
If the system is a ftp server you may want to try switching the mirror write cache off. It could improve write speed. But may impact read.
Looking at your sar output I would expect the two disks in the mirror to have the same amount of r+w. But if you are doing maily reads it MAy be that one disk is "answering" more frequently than the other. (I'm on thin ice here) Could also be a HW issue as SEP points out.
Regards,
Trond
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тАО04-25-2005 06:50 PM
тАО04-25-2005 06:50 PM
Re: Mirror UX performance issue
The Oracle redo logs are creating most of the I/O. Most of the activity would be sequential writes to the same files. In Oracle I see high log_file_sync waits indicating the that the system is waiting to write to disk. That is the original problem that uncovered this issue.
JL
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тАО04-25-2005 07:17 PM
тАО04-25-2005 07:17 PM
Re: Mirror UX performance issue
Out of interest does vmstat show many page-outs occuring at the same time?
Do you have glance installed on this box? It will give a much better view of performance than sar does.
HTH
Duncan
I am an HPE Employee