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Re: Do Disk Heads Stay in the Begining or Middle of a disk when idle ?

From: Martin Doherty <martin.doherty_at_oracle.com>
Date: Wed, 03 Jul 2002 16:28:11 -0700
Message-ID: <3D23888B.B4BC7F6A@oracle.com>


I'm reminded of a story one of our lecturers told us in college, of a bank who in the 1960's developed an online branch network (using IBM hardware - of course!) and was able to obtain blazingly fast response times for account queries and transactions by virtue of their technique of issuing account numbers to their customers that were basically the physical volume:track:sector address where the customer account record was stored!

Everyone was happy, until it came time to upgrade their disk drives to a later model ..... UH OH!

My hunch is that the disk heads would return to the halfway point when idle, to smooth out the seek times (so no track is more than half a disk away). This seems like a 'best practice' to me, but I think it's ultimately up to each disk manufacturer how their device works.

Martin

Bass Chorng wrote:

> In ixroa Steve Adams' Disk Configuration for Online Redo Logs, he stated
> that log files should be located in the begining of a disk to minimize
> disk arm movement.
>
> In IBM's Shark documentation, it states that log files should be located
> in the middle of a disk to minimize access time.
>
> Years ago, I remember Informix DBA guide stated that the physical logs
> ( = rollback segments) and logical logs ( = redo) should be located in the
> middle of a disk because disk heads hover above the middle section of
> a disk once it is powered on.
>
> Does anybody know which is right ? Or does it depend on the disk manufacturer
> ( I really doubt that though ) ?


Received on Wed Jul 03 2002 - 18:28:11 CDT

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