Solved

Cylinder Skewing vs Defragmentation

Posted on 2002-03-22
4
527 Views
Last Modified: 2008-03-06
"Cylinder skewing" technique was surpose to improve Hdd performance by reducing the disk time lost during normal head steps , which  identify and read the desired information from a track within one disk rotation. So why do a "defragmentation" to bring the scattered data around the cylinder to a contiguous position i.e. data on same track  / sector when "cylinder skewing"  make  data saved on different track / sector.

0
Comment
Question by:hhheng
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
4 Comments
 
LVL 32

Accepted Solution

by:
jhance earned 50 total points
ID: 6888752
These days cylinder skewing is done in the physical formatting of the drive by the manufacturer.  In the old days the interface to the drive was very low level and you could optimize drive performance by knowing a bit about how the drive worked and how your operating system performed.

These days the disk access is at a much higher level and the controller is embedded in the drive.  The drives today also have cache memory and are setup with various read-ahead and write-later schemes to makes things go faster.

So the concept of cylinder skewing is not rally applicable any longer.  In fact you could possible slow things down by trying to do such a thing since there are so many levels of buffereing and caching between you and the data on the drive.
0
 
LVL 2

Expert Comment

by:highstar1
ID: 6889289
"Cylinder skewing" Do you mean the disk Interleave Ratio
Or simular techniques to reduce the amount of time the
disk has to wait for the data to come under the R/W heads?

Those are Hardware level processes that have little to do
with the Operating System Software Level Defragmentation.

Defrag trys to move all the data of a single file into
contiguous series of addresses in the fat,vtoc or supernode of your High level disk structure.

You might say your "Cylinder skewing" is to your
low level formated disk structure, what defrag is to
your high level formated disk structure.

You use both, not one or the other.

Many modern Harddrives are now fast enough that they
can be effecient with a 1:1 ratio. Changing the lowlevel
characteristics makes no change in performance of the drive. This is do to the slowness of the overhead of the
drivers, O/S and applications being run.

A 15000 RPM SCSI fast/wide is less likely to need adjusting than a 5400 RPM old IDE drive.


0
 
LVL 32

Expert Comment

by:jhance
ID: 6889672
>>effecient with a 1:1 ratio.

Let me point out that the term "1:1 ratio" refers to SECTOR INTERLEAVE and NOT cylinder skew.  These are DIFFERENT things but somewhat related.
0
 

Author Comment

by:hhheng
ID: 6890195
Agree with jhance about interleave which applies to Sector while Cylinder skewing applies to Track.

For example, if a drive reads a sector and skips a sector to reach the next sequential sector, interleave factor would be 1:3 and so on.

As I understand it , defragmentation is gathering of data scatter over different tracks/sectors so that data are placed in interleave ration of 1:1 and on contiguous track.

Thanks and cheers...
0

Featured Post

Ransomware-A Revenue Bonanza for Service Providers

Ransomware – malware that gets on your customers’ computers, encrypts their data, and extorts a hefty ransom for the decryption keys – is a surging new threat.  The purpose of this eBook is to educate the reader about ransomware attacks.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
CPU Fan stuck on high after running diagnostics on Dell PowerEdge T320 5 111
Quieter Keyboard 6 79
Calibrating x & y screen  pixel coordinates 1 63
Server can not boot up 10 76
The Rasberry PI is a low cost piece of hardware that you can have a lot of fun with through experimenting and building/working on projects like media players, running a low cost computer, build data loggers etc. - see: https://www.raspberrypi.org
Stuck in voice control mode on your Amazon Firestick?  Here is how to turn it off!!!
Exchange organizations may use the Journaling Agent of the Transport Service to archive messages going through Exchange. However, if the Transport Service is integrated with some email content management application (such as an antispam), the admini…
Are you ready to implement Active Directory best practices without reading 300+ pages? You're in luck. In this webinar hosted by Skyport Systems, you gain insight into Microsoft's latest comprehensive guide, with tips on the best and easiest way…

735 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question