How to align the hard disk

  • Thread starter Thread starter Rayees
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R

Rayees

Hi

I have a IO performance problem while I'm using SAP frontend at my Windows
XP PC.

While contacting SAP, they said that this was due to misaligned disk.

They said. Go to "Windows System Information" (command line: winmsd). Open
"Components" / "Storage" / "Disks". You will find a "Partition starting

offset" or "Starting offset" in the list. The value has to be 64 * 512

(32,768), the default is unfortunately 63 * 512 (32,256)."

My question is how to change Partition starting offset value to 32768
instead of 3225

6.



Regards

Rayees
 
Rayees said:
Hi

I have a IO performance problem while I'm using SAP frontend at my Windows
XP PC.

While contacting SAP, they said that this was due to misaligned disk.

They said. Go to "Windows System Information" (command line: winmsd). Open
"Components" / "Storage" / "Disks". You will find a "Partition starting
offset" or "Starting offset" in the list. The value has to be 64 * 512
(32,768), the default is unfortunately 63 * 512 (32,256)."

My question is how to change Partition starting offset value to 32768
instead of 32256.

Regards

Rayees
Click to expand...

This is the manual, for a tool previously known as PowerQuest PartitionMagic.
Symantec now owns it.

ftp://ftp.symantec.com/public/english_us_canada/products/norton_partitionmagic/npmagic_8/manuals/norton_partitionmagic_8.pdf

Note some of the comments here:

http://en.wikipedia.org/wiki/Talk:Cylinder-head-sector

"The History section here is obviously a bit out of date, since CHS tuples
haven't actually corresponded to disk hardware in a very long time!"

I doubt very much, that you can establish a relationship between physical
cylinders on a disk, and the logical addressing used to access them.

From this page, you can download PartInNT.zip . That program displays
disk geometry. The "NT" version would be good for WinXP/Win2K.

http://service1.symantec.com/Support/powerquest.nsf/pfdocs/2004073190203662
( ftp://ftp.symantec.com/public/english_us_canada/tools/pq/utilities/PartInNT.zip )

If you unzip the file, and execute the program, it will display the partitioning
info for the disk. The "sectors per track" is defined as 63 (as part of being a
"large drive placeholder" for escaping the arithmetic bounds of CHS geometry). If
the declaration is 63 sectors per track, then the first track contains sectors
0 through 62, and the next cylinder will begin at 63. It is possible, even when
using PartitionMagic, that it will not allow you to start the partition offset
from the cylinder boundary. So, I guess my issue with the information you've
been given is "64 * 512" is actually "63 * 512" as far as the large drive
placeholder values of geometry are concerned. The physical disk does not have
63 actual sectors per track, but some other value. And that value, may not
even be stated in the available information for the hard drive.

To prove the point, if I use PartInNT to look at the "total sectors" in my C:
partition on my 80GB drive, the sector count is 156280257. That number is
evenly divisible by 63, not 64. 63 * 2480639 = 156280257, so there are
2480639 tracks in my C partition, exactly. Thus the starting sector number
of 63, is not an error, and not something to fool with. In my opinion.

I think the information you've been given, might have been valid
20 years ago, but not now. But I'm not an expert. You should visit
comp.sys.ibm.pc.hardware.storage and ask someone there to review
the advice you've been given and give comments. I think SAP is putting
you to a lot of trouble for nothing.

Paul
 
Paul said:
If the declaration is 63 sectors per track, then the first track
contains sectors 0 through 62, and the next track will begin at 63.
It is possible, even when using PartitionMagic, that it will not
allow you to start the partition offset from the track boundary.
Click to expand...

The word "cylinder" in the previous section, should have been "track".

Paul
 
Whatever you do to fix the issue, make certain that you make an image backup
of the drive before you make the changes. This way if something goes wrong
and you can no longer access the drive, you will at least have a way back.

JS
 
After he makes an image of his drive, I would boot from a CD or floppy,
run FDISK to recreate the partition and then format the drive. That
should clean things up. Restore the image and off you go.

-Jim
 
Hello Ray,

Thank you for using newsgroup!

From your post, I'd like to thanks Paul, JS and Jim's great information
sharing with us.

Thanks & Regards,

Ken Zhao

Microsoft Online Support
Microsoft Global Technical Support Center

Get Secure! - www.microsoft.com/security <http://www.microsoft.com/security>
====================================================
When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.
====================================================
This posting is provided "AS IS" with no warranties, and confers no rights.
 
Dear Paul, JS and Jim

Thanks for your valuable information.

I will do the testing in a PC and get back to you.

I read in some article on how to change the partion offset value throrugh
diskpart.exe, but that doesn't seems to work. Anyway i will try this out.

Regards
Rayees
 
You're welcome Ken and Rayees.

JS

Rayees said:
Dear Paul, JS and Jim

Thanks for your valuable information.

I will do the testing in a PC and get back to you.

I read in some article on how to change the partion offset value throrugh
diskpart.exe, but that doesn't seems to work. Anyway i will try this out.

Regards
Rayees

"Ken Zhao [MSFT]" said:
Hello Ray,

Thank you for using newsgroup!

From your post, I'd like to thanks Paul, JS and Jim's great information
sharing with us.

Thanks & Regards,

Ken Zhao

Microsoft Online Support
Microsoft Global Technical Support Center

Get Secure! - www.microsoft.com/security
<http://www.microsoft.com/security>
====================================================
When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.
====================================================
This posting is provided "AS IS" with no warranties, and confers no
rights.
Click to expand...
Click to expand...
 
Hi Paul

The information is really great.

I understood upto certain extent, I downloaded PartinNT and say the disk
geometry.

I have query here. I have 60GB HDD and I have two partition. C: is Primary
and D:\ is extended partition.

When I run Winmsd --> Storage --> Disk. I saw Partition starting Offset
information for Disk 0 partition 0 is 32256 bytes where as Disk 0 partion 1
is 27,085,847,040 bytes.

If my objective is to change the partition starting offset from 32256 to
32768 (as per SAP), and I have constraints in doing that, on what basis Disk
0 Partition 1 value is so high.

I'm not ver clear, since I lack basic knowledge in this subject. Will be
greatful, if you can guide me please.

Regards
Rayees
 
Rayees said:
Hi Paul

The information is really great.

I understood upto certain extent, I downloaded PartinNT and say the disk
geometry.

I have query here. I have 60GB HDD and I have two partition. C: is Primary
and D:\ is extended partition.

When I run Winmsd --> Storage --> Disk. I saw Partition starting Offset
information for Disk 0 partition 0 is 32256 bytes where as Disk 0 partion 1
is 27,085,847,040 bytes.

If my objective is to change the partition starting offset from 32256 to
32768 (as per SAP), and I have constraints in doing that, on what basis Disk
0 Partition 1 value is so high.

I'm not ver clear, since I lack basic knowledge in this subject. Will be
greatful, if you can guide me please.

Regards
Rayees
Click to expand...

OK, I tried a little experiment.

I installed my copy of Partition Magic 7 (PowerQuest version) and tested
on a brand new disk. The geometry of my disk is 9729 cylinders, 255 heads, 63 sectors
(an 80GB disk).

If I use Partition Magic, it allows a partition to start at sector 63 (not 64).
If I use the "Move" option, to reposition the partition, the partition moves
in increments of 7.8MB!. Moving the partition by single sectors is not allowed!
The partition can start at sector 63, or at sector 63 + 255*63 etc. The last
value is "sector 63 plus one cylinder" of the fake geometry. I am not allowed to
add just one sector.

I looked up the interface of the RedHat Linux partitioning tool. You can
see here, that the partition offset field in the tool, is in units of
cylinders, and not sectors. Thus, you cannot do it in Linux either. The
Linux tool behaves the same way that PartitionMagic does.

http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/install-guide/s1-diskpartitioning.html

The disk no longer has a geometry. The 9729/266/63 value, satisfies the
traditional interface, until the operating system is running. Once running,
as far as I know, the disk and OS talk "LBA" or logical block addresses,
and those are a simple sector number. (I even looked up in the ATAPI spec,
and while "cylinder" is defined in the terminology section, it does not
appear in the body of the specification itself. So CHS is obsolete.)

http://www.t13.org/FTPSite/Default.aspx (get the userid/password here first)
ftp://ftp.t13.org/docs2002/d1532v1r1a-ATA-ATAPI-7.pdf (then check this document)
ftp://ftp.t13.org/docs2002/d1532v2r1a-ATA-ATAPI-7.pdf

For a primer on disk geometry, try this storagereview article.

http://www.storagereview.com/guide2000/ref/hdd/bios/sizeOlder.html

Also, for another experiment, download HDTach, and run the "long bench".
Click "long bench" and the click "Run Test". The resulting stair step
curve, shows how the actual geometry inside the disk is "zoned" and
is not of a constant density. Thus, the SAP idea, of aligning the disk,
is just foolish. If each zone has a different number of sectors, then
no performance optimization by means of sector offset, is feasable.

http://www.simplisoftware.com/Public/index.php?request=HdTach

Summary:

As near as I can tell, the SAP advice you've been given is *wrong*.

Hope that helps,
Paul
 
Thanks a lot Paul.

The information you gave is amazing, with all these data now I can question
SAP.

Once again thanks a lot for such wonderful and detailed information.

Regards
Rayees
 
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