[dba-Tech] Performance in disc partitions

DJK(John) Robinson djkr at msn.com
Mon Jan 28 06:01:08 CST 2008


Well, *IF* the outer track holds more than the inner track, then you get
more data passing the head in one revolution, giving higher transfer rate
and fewer seeks - so lower access times overall.  But there's still that
*IF*.

CDs are different, of course, with their variable speeds.

John


-----Original Message-----
From: dba-tech-bounces at databaseadvisors.com
[mailto:dba-tech-bounces at databaseadvisors.com] On Behalf Of Erwin Craps - IT
Helps
Sent: 28 January 2008 10:18
To: Discussion of Hardware and Software issues
Subject: Re: [dba-Tech] Performance in disc partitions


The edge of the disk also means lower access times.
I don't know why because RPM is the same at the inner as outer side of the
disk.

I know that CD drives change their RPM speed depending how far they are on
the inner and outer side of a cd so the laser can keep up reading the data,
don't know if that is true for HD. That could be an explanation for lower
access times, because it takes longer for the data to pass the head.


You can check http://www.hdtune.com/ it's a free disk performance check, it
will show you the transfer rate / access time for your disk over the whole
disk.

Erwin




-----Original Message-----
From: dba-tech-bounces at databaseadvisors.com
[mailto:dba-tech-bounces at databaseadvisors.com] On Behalf Of DJK(John)
Robinson
Sent: Monday, January 28, 2008 10:34 AM
To: 'Discussion of Hardware and Software issues'
Subject: Re: [dba-Tech] Performance in disc partitions

Thanks, John.  That would suggest higher transfer rates nearer the edge,
with some cylinders holding more than others.

Has anyone got any good links to this sort of stuff?

Oh, and of course I'm still interested in knowing whether the 'first'
partition is nearer the edge or the spindle...

John


-----Original Message-----
From: dba-tech-bounces at databaseadvisors.com
[mailto:dba-tech-bounces at databaseadvisors.com] On Behalf Of jwcolby
Sent: 28 January 2008 00:57
To: 'Discussion of Hardware and Software issues'
Subject: Re: [dba-Tech] Performance in disc partitions


IIRC, the disk controller speeds up the writes as the tracks move outwards
towards the edge of the platter.  IOW there is more surface area on the
outer tracks so they just bump up the waveform to allow more data to be
written in that larger surface area.  When thought of from that perspective,
the outer tracks hold more data / track and so may require less head
movement. I have no idea whether the first volume is on the inner tracks or
the outer tracks.


John W. Colby
Colby Consulting
www.ColbyConsulting.com 
-----Original Message-----
From: dba-tech-bounces at databaseadvisors.com
[mailto:dba-tech-bounces at databaseadvisors.com] On Behalf Of DJK(John)
Robinson
Sent: Sunday, January 27, 2008 7:47 PM
To: 'Discussion of Hardware and Software issues'
Subject: [dba-Tech] Performance in disc partitions

I am about to partition a new disc.  One partition will be very active in
terms of reads and writes, another almost dormant.

Is there any advantage in performance terms in having the active partition
as the 'first' one on the disc?  Or the last one?

It's a long time since I was involved in disc layout at a low level, and I'm
wondering whether 'cylinders' these days are still all the same size, with
the data near the edge of the platter just more spread out than that near
the spindle - or not?

TIA
John


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