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RE: High disk capacity dangers

From: <>
Date: Tue, 6 Jun 2006 07:39:03 -0500
Message-ID: <>

Sometimes, ideas that sound funny come from what I call "the lost parameter." It's like the story at

One really good reason not to keep a disk full is that if a disk receives so many I/O requests per second that performance suffers, then one way to fix it is to move bytes off that disk to make it "less interesting" to so many users.

But if someone forgets why they moved bytes off a disk once upon a time, then it begins to look like a rule saying you should never keep a disk more than x% full.

Another reason to keep a disk partly empty is to ensure that the OS file extent manager has some space to work in. But if you're using a disk solely for Oracle data files that don't often grow or shrink, then you don't need to leave the elbow room.

Of course, the SA could have some perfectly legitimate reason that I've never heard of. To quote Deborah Holland, "Talking is good."

Cary Millsap
Hotsos Enterprises, Ltd.
Nullius in verba  

Hotsos Symposium 2007 / March 4-8 / Dallas Visit for curriculum and schedule details...

-----Original Message-----

[] On Behalf Of Mercadante, Thomas F (LABOR)
Sent: Tuesday, June 06, 2006 7:13 AM
To:; Subject: RE: High disk capacity dangers

I'd be curious to know what number he feels is "ok". 90%? And why?

-----Original Message-----

[] On Behalf Of Fred Smith Sent: Tuesday, June 06, 2006 8:05 AM
Subject: High disk capacity dangers

Just wanted to run this by everyone here, I have a database on HP-UX. Some of my read only tablespaces are on a physical disk that I keep
at about 99% capacity (it's not going to grow obviously, it's read-only).
The new Unix SA is saying that it's unacceptable and dangerous to keep a

disk at 98,99, or 100% capacity. I always thought it could be even at 100%
capacity without any problems.

Is there any reason that anyone knows of as to why a disk should not be at
99% or 100% capacity?

Thank you!

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-- Received on Tue Jun 06 2006 - 07:39:03 CDT

Original text of this message